No. 61 - September 1990

Portugal and ESO Sign Cooperation Agreement

1 To some of the experienced diplo- the beginning of a new, interactive era Government "will, allocate an amount mats in the attentive audience, the fes- with high expectations. equivalent to a percentage of the annual tive ceremony on July 10, 1990, may On a hot summer's day in Lisbon, the contribution Portugal would have to have been just another of the steps to- Republic of Portugal and the European pay, if it was already a member of ESO, wards European integration, now being Southern Observatory signed a Cooper- to the development of research in the taken all over the continent. But for the ation Agreement which is aimed at full field of contemporary Astronomy, so as astronomers from Portugal and ESO, membership of Portugal in ESO within to permit a future efficient usage of this official act was much more than the next ten years. ESO's facilities by Portuguese as- that; it was a joyous event that marked During this period, the Portuguese tronomers". This amount will be spent

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At the signing ceremony in Lisbon. From left to right: Professor Teresa Lago (Astrophysical Centre, Porto), Professor Harry van der Laan (ESO Director General), Professor Jose Pedro Sucena Paiva (Portuguese Secretary of State for Science and Technology), Professor Carlos Salema (President of JNICT), Mr. Fernando Gonqalves (Chief of Cabinet of the Secretary of State). A 1 on a number of infrastructures Council in December 1989. In this connection, significant support is necessary for the development of As- The ceremony commenced with the now becoming available, especially tronomy in Portugal and on technologi- showing of a short video film about ESO after Portugal became a full member of cal and scientific training actions related and its role in European astronomy. Pro- the European Community. In its present to ESO's activities. fessor Lago then commented on the quest for development, Portugal can In return, Portuguese astronomers will present situation in Portuguese as- draw inspiration from the Great Maritime have access to ESO's facilities during tronomy. It is in a critical period of Discoveries in earlier centuries. the pre-accession period under scien- growth, for which the association with In the afternoon, the Director General tific conditions similar to those of ESO will be a great support and and his small ESO delegation went to Member Countries. It is expected that stimulus. The full text of the speech is Porto to visit the University and its Centre the OPC will soon receive the first pro- reproduced on the next page; see also for Astrophysics, which was officially posal(~)from Portugal, and that some the summary on page 4. started here last year. Since 1984, when joint programmes with astronomers Following the solemn act of signature, a programme for astronomical studies from ESO member countries will be Professor van der Laan expressed his was first developed in Porto, there has worked out before the end of the year. great pleasure in connection with the been an increasing interest and a steadi- A Joint Portuguese/ESO Advisory new association between Portugal and ly growing number of students in this Body is being set up to monitor the ESO. He expressed his conviction that discipline. Several Master's degrees development of Portuguese astronomy the ancient astronomical tradition in have been gained abroad and presently, and its interaction with ESO. Portugal, particularly evident at the fa- a number of PhDs are well under way. In The Agreement was signed on behalf mous naval institute founded by Henry a few years, the Porto group can be of the Portuguese Government by His the Navigator and of such a great im- expected to reach the critical mass, Excellency, Secretary of State for Sci- portance for the far-reaching expedi- needed to introduce more, high-level ence and Technology, Prof. Dr. Jose tions of that time, will continue and be courses. For the time being, there is a Pedro Sucena Paiva, and for ESO by its strengthened by the interaction with special interest in stellar studies and Director General, Prof. Dr. Harry van der ESO. He surveyed the ESO facilities and cosmology. The Astronomy Centre is Laan. Among the invited guests were the importance of astronomy, not just as neighbour to the University's Computing high government officials, quite a few a science in its own right, but also as a Centre and many of the students have Portuguese scientists representing driver for new and advanced technology become involved in image processing; other scientific fields, as well as many which may be of great use in many other MlDAS is being implemented. Some stu- media representatives who reported ex- fields as well. He looked forward to the dents have already made short visits to tensively about this event in TV, radio day when a new generation of Portu- the ESO Headquarters. and newspapers. guese astronomers will be able to make It is obvious that Portuguese as- Joining the Secretary of State and the full use of their new opportunities within tronomy is in a phase of rapid and well Director General on the platform were the European astronomical community considered expansion. With access to the President of Junta Nacional de In- and when Portugal will become a the ESO telescopes, more young as- vestiga~so Cientifica e Technologica Member State of ESO. tronomers in this country will be drawn (JNICT: National Board for Science and In his discourse (English translation towards observational studies and their Technological Research), Prof. Dr. Car- hereafter), the Secretary of State em- possibilities for fruitful interaction with los Salema, and Prof. Dr. Teresa Lago, phasized the rapid progress in as- astronomers in other places will in- Astrophysical Centre of the University of tronomy, in particular because of mod- crease. And in ten years' time, or Porto, both of whom played key roles ern technology. He stressed the impor- perhaps even before, the formal adher- during the extensive preparations that tance attached by his country to the ence of Portugal to ESO will follow preceded the conclusion of this Agree- furthering of scientific and technological naturally, with the full, mutual benefits. ment, which was approved by the ESO projects within a European framework. The Editor

Speech by Professor Jose Pedro Sucena Paiva

It is indeed a great pleasure and namely through advanced training of Until the 17th century, astronomy was privilege for me to sign on behalf of the human resources, so that the number of largely concerned with the measure- Portuguese Government the Coopera- Portuguese astronomers becomes, in ment of the positions and motions of the tion Agreement between the Republic of proportion to the scientific community, Sun, Moon, planets, and apparently fix-

Portugal and the European Organization comparable to that of the ESO Member ' ed stars visible to the unaided eye. Then for Astronomical Research in the South- States. ESO will provide access to its the laws of planetary motion were dis- ern Hemisphere - ESO -, a prestigious facilities to Portuguese scientists and covered, the telescope was invented, international organization devoted to graduate students under scientific con- and the laws underlying motion and scientific research in the field of As- ditions similar to those of the Member gravitation were formulated. tronomy. States. In the 18th century the first ideas I firmly believe that this Agreement, Man has always endeavoured to based on extensive observations of the which sets the conditions for Portugal's study the objects outside planet Earth structure of the Galaxy that contains the adhesion to ESO within a ten-year and its immediate environment, includ- ,Earth and of the Universe were put for- period, will prove to be a decisive mile- ing the Moon, Sun, planets, stars, ward. stone for the development of Astronomy the Galaxy and similar external The 19th century brought the intro- and Astrophysics in this country. star systems, interplanetary and inter- duction of two basic techniques, spec- During this period Portugal will rein- stellar matter, and the Universe as a troscopy and photography, which led to force its scientific capability in this field, whole. new and quantitative methods for measuring the quantity and quality of Earth for the benefit of ourselves and the and making their life somewhat difficult. light and enable physical studies to be future generations. No generation has a But there are some good prospects on made of the brightness, temperatures freehold on this planet, all we have is a the horizon to overcome this solution. and chemical nature of the stars and life tenancy, with a full repairing lease. In the framework of the Structural nebulae. Science and Technology are now be- Funds Reform of the EC, Portugal has Theoretical analysis of the contribu- ing seriously considered in this country submitted a Programme - emblemati- tion of the stars advanced enormously at the political level. After many years of cally named the Science Programme - in the 20th century through the devel- relative neglect, our scientific communi- designed to create new scientific infra- opment of quantum theory and other ty is now the object of considerable structures, reinforce existing ones and branches of physics, leading to a new attention and care. Conditions for scien- train new scientists. The programme, discipline: astrophysics. tific research and technological de- which was extremely well received by Astronomy now flourishes as never velopment have considerably improved the EC Commission and approved with before: quasars and pulsars have been in recent years, especially since Portu- minor alterations, is now in the first discovered and there are hopes that gal's integration in the European Com- stage of execution. answers to problems such as the origin munity in 1986. The articulation of this Programme of the Universe, of chemical elements, At the turning point that Portugal is with the new EC Framework Programme of the Earth, and of life itself may be now, Science and Technology are key 1990194 will certainly provide the stage found. ingredients for our development and full for a rapid development of Portuguese The present development of As- participation in the construction of Science and Technology. It is up to the tronomy is to a large extent due to the Europe. scientific community to seize the oppor- use of modern technology, namely ad- International contacts are being tunities available to them. The govern- vanced telecommunications, electronic strengthened rapidly and our scientists ment should only create the right envi- computers, precise timekeeping and and engineers are involved in a sizable ronment and of course adequate condi- rocketry. number of multinational R & D projects, tions and then step aside and in due This is also the case in other areas of namely in the context of the European time evaluate the results. fundamental research, the advance of Community Framework Programme. The private sector should be called which in effect many times requires the The scientific communities of the dif- upon to participate more actively in the development of advanced technologies, ferent countries are certainly among the R & D activities. We understand that for which can partly justify the heavy invest- most internationalized bodies of the a small or medium enterprise, R & D is a ment necessary to provide the adequate society, for obvious reasons. Science very expensive activity. That is why Uni- facilities. has always cut across barriers and fron- versity-Industry partnerships should be The risks involved in big science pro- tiers and international contacts are strongly encouraged and it pleases me jects are not negligible, as the recent instrumental for its development. Inter- to say that some encouraging examples mishap with the Hubble Space Tele- nationalization and mobility of scientists have already flourished in this country. scope well demonstrates. However, the is therefore a cornerstone of our scien- In its present quest for development, potential rewards are enormous, since tific policy. Portugal can draw inspiration to the the intrinsic value of knowledge itself is The Portuguese Scientific Community Great Maritime Discoveries of the 15th invaluable and priceless. is still relatively small - about 5000 full- and 16th centuries, which were possible The sight of our beautiful planet from time equivalent scientists - but young, by the conjugation of four factors: (1) space has made us fully aware of its competent and dynamic. This number political will; (2) rigorous and methodic smallness and fragility. Technology can has to be rapidly increased, both by new scientific knowledge; (3) enterprising in some way be defined as the means entry-level recruits and also by attract- spirit and the capacity of taking risks; (4) through which man manipulates the en- ing senior foreign scientists. mastery of the technological systems of vironment. This definition clearly shows At this stage, our infrastructures - that time, navigation and weaponry. that, despite its tremendous achieve- buildings, equipment and support per- The challenges which confront us ments, technology must be used in a sonnel - are still insufficient, limiting nowadays require the same ingredients way compatible with the survival of many times the efforts of our scientists for an adequate response.

Speech by Professor Teresa Lago

I believe today is indeed an important and university authorities. Astronomy situation at the, until then, unique State- mark in the development of Astronomy was, for the very first time, considered or University-financed Institutions for as- in Portugal. In the present times of as one of the areas that should be de- tronomical activity. Although this is awareness for Science and Technology, veloped. neither the place nor the time to com- 'today's events are of indisputable im- Of equal importance was the simul- ment on those results, they should, even portance for the future of Astronomy, taneous survey of the situation at the today, be given serious and urgent atten- both in research and education. Portuguese Observatories - the first tion. Qualified human resources are the They come in the sequence of an done in modern times - including a full crucial component, otherwise all efforts initiative taken by JNlCT in 1987, and enquiry on the facilities, personnel, activ- are condemned to failure. the subsequent proposal for a nation- ity (teaching and research), programmes The situation of Astronomy in Portu- wide programme for the development of and projects being carried out at the gal remains very worrysome: instead of AstronomylAstropysics. JNICT's initia- three University Observatories (Porto, the "European average" of 10 to 20 as- tive was then very important for As- Coimbra and Lisboa) and at the National tronomersl1,000,000 inhabitants, we tronomy, always forgotten or merely Observatory (Lisboa). The conclusions of are still short by a factor of 1O! And the tolerated both by research planners this survey gave a realistic image of the lack of long tradition of research work in the field has made recovery more number of temporary positions, both at credit it fully deserves and receives in difficult. the technical support level and post- other countries in Europe. I take this The situation has substantially im- doctoral level (national and/or foreign) ceremony as a real commitment for a proved over the last two years. Some so that research teams can be provided continuous and serious effort to develop investment has been made. However, with acceptable working conditions; at a Astronomy in Portugal. A commitment any programme for the development in more advanced phase an adequate to provide conditions that allow the Por- Astronomy must necessarily include number of permanent research posi- tuguese astronomy to grow to levels simultaneous components, risking to tions for Astronomy should also be con- comparable to the European ones over compromise the objectives aimed at, sidered, a period of time of 5 to 10 years. would any of them be neglected. These (iv) finally the access to adequate ob- I want to thank the Secretary of State components are serving facilities for Portuguese as- for Science and Technology for his deci- (i) the education of a new generation tronomers and postgraduate students. sive support and involvement at the cru- of astronomers, both at University level The signature of this agreement with cial stages of the negotiations with ESO. and at doctoral level. At the doctoral ESO is an event of great importance for And to express to the ESO Director level this should preferably take place the development of the astronomical re- General my gratitude for his com- abroad or through international col- search in Portugal. Not only does it fulfil prehension and understanding, that has laborative projects, until a "critical some of our needs -the access to ade- been so important for the conclusion of mass" is achieved; this implies a steady quate observing facilities - but it also such an advantageous agreement for number of grants for some period of allows the collaboration and, at some us. I feel that Prof. van der Laan's time, level, participation with ESO at an excit- attitude during the whole process was (ii) the support of a small number of ing time -the time in which a very large closer to the fellow astronomer and well infrastructures, providing the necessary telescope of a new generation and the beyond the negotiator's job. facilities for research and education, important related instrumentation are Of course, years of low profile take and the support to those fields where being developed at ESO. time and an enormous effort to be re- competitive work is already being done, I believe this agreement constitutes placed. Mentalities probably take even in order to avoid dispersion of the avail- the undeniable proof that the decision longer to change. But as an astronomer able resources, makers in Science and Technology in I must say this is a time of optimism and (iii) the establishment of a small Portugal finally give to Astronomy the strong hopes for a brighter future.

A Short Summary of Astronomy at "Centro de Astrofisica da Universidade do Porto" M. T. LAGO, Astrophysical Centre, University of Porto, Portugal

In 1988 JNlCT (the national research part-time research, and 1 sec- conditions for its visitors to collaborate council) took the decision to finance the retaryllibrarian). in the undergraduate teaching and to first research centre in Astrophysics in It also involves several undergraduate involve the terminal year students in its Portugal, the "Centro de Astrofisica" at students of Astronomy (terminal year). projects. Therefore the Centro's support the University of Porto. Because of the particular situation of for education comes, Although in activity since 1988 the Astronomy in Portugal, we believe that - at university level: through support Centro was officially created in May any programme aimed at the develop- to the only undergraduate degree in the 1989 as a financially autonomous ment of Astronomy must necessarily in- country aimed at the education of the association within the University and is clude five simultaneous components. new astronomers, at the School of Sci- housed since October 1989 at the new There would be a risk of compromising ences of the University of Porto; this building of the University Computer the objectives if any of them would be interdisciplinary degree was set up in Centre. neglected; the "Centro de Astrofisica" 1984 and is jointly offered by the Phys- As personnel it involves therefore includes all of these compo- ics and Applied Mathematics Depart- - 2 University staff (Ph.D. in As- nents in its objectives: ments. It has a four-year plan of studies, tronomy, 1979, 1982), 1. The education of a new generation a numerus clausus of 15 students per - 8 Ph. D. Students (I M.Sc. in Applied of astronomers - the shortage of ade- year and is structured in course units of Statistics, 1988; 2 M.Sc. in As- quately trained and active prospective which 37% are in Physics, 32% in tronomy, 1989, 1990; 1 M.Sc. in supervisors in Astronomy in Portugal Mathematics, 25% in Astronomy and Astronomical Technology, 1989; 3 implies that, at this initial stage, the ma- 6% either in Chemistry, Geology, D. E.A. in "Astrophysique et Tech- jority of the doctorates must be pre- Mathematics or Physics. The initial three niques Spatiales", 1989, 1990; 1 pared abroad, and those to be prepared years providing basic training in "Licenciado" in Surveying En- at home also need to benefit from a Mathematics and Physics, except for an gineering, Univ. Porto, 1984) and close and continuous collaboration with introductory course (first year) intended - 2 temporary staff (1 "Licenciado" in scientists from well-known foreign in- as an overview of modern Astronomy PhysicsIApplied Mathematics [As- stitutions; therefore the Centro has been and aiming at keeping alive the stu- tronomy, University of Porto, 19891 trying to guarantee a continuous and dent's enthusiasm. The 3rd year offers a in charge of the computer manage- equilibrated scheme of grants as well as general Astronomy course and finally ment and assistance to users, gen- the necessary contacts. the 4th year includes 5 options from an eral administrative activities and At the same time, the Centro provides annual list of various topics in As- tronomy, naturally strongly dependent postgraduate education, undergraduate 3.1 - library facilities (a collection of on the availability of lecturers (local and education, the promotion of Astronomy back numbers of the most relevant jour- visiting). An example of such a list in- (through the organization of con- nals was generously offered by some cludes Astrometry, Cosmology, Ex- ferences, courses, etc.) and the stimula- Institutions such as ESA, ESO, Utrecht tragalactic Astronomy, Formation and tion of science popularization. Laboratory for Space Research, Obser- Evolution of Stars and Stellar Structure. The ongoing research projects at the vatoire de Meudon, Royal Greenwich Some of these courses are fully deli- Centro are in the following areas: Observatory and astronomers working vered (or include units of 10 to 15 hours) (a) - "Classification of Observed As- there), by visiting professors or researchers; trophysical Structures" 3.2 - computer facilities for data this has proven to be very stimulating, (b) - "Cosmology - Jordan-Thiry analysis, access to networks, data exposing the students to different peo- theories and models of galactic forma- banks, data bases and larger computers ple and also helping to compensate for tion", existing in the country, as well as ade- the lack of "people around", considering (c) - "Stellar Astrophysics". quate software; the Centro is equipped that the number of astronomers in Por- These areas have been selected be- with a CI. Vax 3400,700 MB in disk TK 70 tugal is presently so reduced - well be- cause they were already active research and accessories such as graphic termi- low the European average of 1 to 2 areas at the University of Porto and all nals, printer, lmage Display device and astronomers per 100,000 inhabitants; have research projects where Ph.D. adequate software is also available - at a younger level: taking As- work is carried on, namely: (Starlink, Nag, Matlab and MlDAS being tronomy to the Schools through a pro- (a) - "Classification of Observed As- installed); some Mackintosh are also gramme involving the Centro, the Re- trophysical Structures" - the quantita- available. gional Education Authority and the Gov- tive analysis and application of statisti- 4. Observing facilities - the availability ernment Local Authority; this includes cal methods to the study of large struc- of observing facilities, either national or sessions with a portable planetarium ture and their origins, a collaborative on a collaborative basis with internation- ,,Starlab" donated to the Centro by the project with people at ESO and the ST- al observatories, for the Portuguese as- Government Local Authority (the ECF involving one Ph. D. student, tronomers and post-graduate students planetarium sessions are prepared for (b) - "Cosmology" - the study of is vital; besides the existence of poten- age groups 5-7, 8-10 and 10-12), dark matter in the Universe, involving tially very good sites on the national talks on various topics of Astronomy one Ph.D. student at the Centro, territory, such as Madeira, and the and the preparation of slide sets with (c) - "Stellar Astrophysics" possibility of building a national obser- explicative texts to be lent to teachers at - the modelling of winds in young vatory being very attractive and not to various levels. stars, a collaborative project with peo- be excluded in the long run, the alterna- The Centro has also been involved in ple at the University of Sussex involving tive of the participation in existing inter- the planning of the Master's degrees for one Ph. D. student at the Centro (1 990), national facilities seemed to be more students connected with it; several stu- - the study of the evolution of pre- advantageous. People from the Centro dents from the Centro have successfully main-sequence stars, a collaborative were deeply involved in all the negotia- completed their degrees at various As- project with people from the Astrofy- tions process that successfully ended in tronomy departments with the following sisch Instituut, Vrije Universiteit Brussel, the present agreement with ESO. thesis: involving one Ph.D. student (1989), 5. Promotion of the popularization of - "The Solar-Stellar Connection", - the study of MHD outflows from Astronomy - the Centro has had various University of Sussex (1989), astrophysical objects, a collaborative initiatives during the current year, name- - "Evolution des Etoiles Bleues et project with people from the Depart- ly through activities such as Lumineuses aux Environs de la Limite ment of Mathematical and Computa- - the local organization of the ESO de Humphreys-Davidson", Universites tional Sciences, University of St. An- exhibition in Porto (October 1990) in- Paris VII et Paris XI (1989), drews (1989), cluding organized visits for students in - "IRIS - A Project on Infrared lmage - the study of the interaction be- the terminal years of Secondary Sharpening", University of Edinburgh tween young stars and molecular Schools, (19891, clouds, involving one Ph. D. student - the organization of a series of pub- - "La Fonction de Luminosite des from the Centro at the Department of lic conferences on several topics of As- Nebuleuses Planetaires", Universites Astronomy of the University of Edin- tronomy simultaneously with the ESO Paris VII et Paris XI (1990), burgh (1989), exhibition, - "L'~H~dans le Soleil, ~tudeAnalyti- - two other Ph.D. students are ex- - various popular-level talks on As- que de la Diffusion Microscopique", pected to start in October Ph.D. pro- tronomy. Universites Paris VII et Paris XI (1990), jects within Stellar Astrophysics. Most of these activities also involve - one thesis to be completed soon, We are also working in order to try to the Astronomy students. Queen Mary and Westfield College - guarantee that at a more advanced University of London (1990). stage temporary post-doctoral positions The University of Porto is also the (2- to 3-year contracts) are available not national node for the European As- only at the Centro but also at other trophysics Doctoral Network, a consor- national Institutions. Furthermore, we tium which today federates 21 European are also trying to draw attention to the Universities all having a graduate pro- fact that if all this effort is to be fully New ESO Scientific gramme in Astrophysics, ESA and ESO. explored it should involve a real commit- This Network has continuously bene- ment by the universities and national Preprints fited from national, European Communi- research authorities towards the open- (June-August 1990) ty (ERASMUS) and European Science ing of permanent positions in As- Foundation support. tronomy at the various Institutions. 705. E. Gosset et al.: A Search for Quasars in 2. The Centro is the institutional struc- 3. The Centro provides the local in- a Field Around NGC 520. M. N. R. A. S. ture providing support for the develop- frastructure to support research, 706. P. Magain and G. Zhao: Empirical ment of research projects, adequate through Study of Departures from the Excitation Equilibrium of Fel in Metal-Poor Stars. Astrophysical Journal. 707. D. Hutsemekers and J. Surdej: Forma- ESO FELLOWSHIPS 1991 -1992 tion of P Cygni Line Profiles in Relativis- tically Expanding Atmospheres. As- The European Southern Observatory (ESO) intends to award up to six post-doctoral trophysical Journal. fellowships tenable in the ESO Headquarters, located in Garching near Munich. 708. T. Baribaud and D. Alloin: On the Use of The main areas of activity are: [OIII] Narrow Line Emission for Scaling - to do research in observational and theoretical astrophysics; Spectrophotometric Data in Active - to carry out a programme of development of instrumentation for the La Silla Galactic Nuclei. Astronomy and As- telescopes; trophysics. - to develop future telescopes involving new technology; 709. A.M. Lagrange-Henri et al.: Search for - to provide data reduction facilities for users of the ESO instruments; Beta Pictoris-Like Stars. Astronomy - to provide photographic facilities for atlases of the southern sky; and Astrophysics, Suppl. - to foster cooperation in astronomy and astrophysics in Europe. 710. L.B. Lucy, I.J. Danziger and C. Fellows normally participate in one or more of the above. In addition there is the Gouiffes: Excitation by Line Coinci- possibility of participating in the activities of the European Coordinating Facility of the dence in the Spectrum of SN 1987A. Space Telescope (ST-ECF) which has been established at ESO. Astronomy and Astrophysics. Fellows will normally be required to spend up to 25% of their time in supporting 71 1. J.S. Chen, X.-W. Liu and M.-Z. Wei: activities such as the introduction of users to data reduction facilities, remote control CCD Photometry of Unclassified operations and testing new instrumentation. Cataclysmic Variable SS UMi (PG Fellowships are to be taken up between January and October 1991. 1551 + 71 9). Astronomy and Astro- Most of the scientists in the Centre come from the member States of ESO, but physics. several are from other countries. The Member States of ESO are: Belgium, Denmark, 712. D. Baade,, W. Schmutz and M. van the Federal Republic of Germany, France, Italy, the Netherlands, Sweden, and Switzer- land. In addition to regular staff members, the Centre comprises visiting scientists, Kerkwijk: Short-Term Activity in the y2 Velorum System: The 0-Type Super- post-doctoral fellows, and graduate students. giant is a Nonradially Pulsating Star. ESO facilities include the La Silla Observatory in Chile with its eight telescopes in the Astronomy and Astrophysics. range 0.9 to 3.6 m, as well as a 1-m Schmidt, the 15-m SEST and smaller instruments. In Garching, extensive measuring, image processing and computing facilities are 713. A.F.M. Moorwood and E. Oliva: Hz available. Emission in Galaxies: Observational Applicants normally should have a doctorate awarded in recent years. The fellow- Constraints on Ultraviolet Excitation. ships are granted for one year, with normally a renewal for a second year and Astronomy and Astrophysics. occasionally a third year. Applications should be submitted to ESO not later than A. F. M. Moorwood and L. Origlia: IR October 15, 1990. Applicants will be notified in December 1990. The ESO Fellowship Images of the Circinus Galaxy and NGC Application form should be used. Three letters of recommendation from persons 4945. To appear in Proceedings of the familiar with the scientific work of the applicant should be sent to ESO directly. These NOAO/KPNO Conference on Astrophy- letters should reach ESO not later than October 15, 1990. sics with lnfrared Arrays. Enquiries, requests for application forms and applications should be addressed to: 714. E. Oliva, A.F.M. Moorwood and I.J. Danziger: lnfrared Spectroscopy of European Southern Observatory Supernova Remnants. II. A Detailed Fellowship Programme Study of RCW 103. Astronomy and As- Karl-Schwarzschild-Str. 2 trophysics. 0-8046 GARCHING b. Miinchen 715. Proceedings of the ESO-CERN Topical Federal Republic of Germany Workshop on "LEP and the Universe". April 5 and 6, 1990. CERN, Geneva, Switzerland. Organized by J. Ellis, P. Salati and P. Shaver. Cosmic Value of H, Freed from All Local 1991 IAU Transactions XXIA, Commis- 716. D. Hutsemekers and E. van Drom: The Velocity Anomalies. Astrophysical sion 47). Supergiant Bep Star CD -42"11721 Journal. 724. P. Molaro and P. Bonifacio: Chemical and Its Surrounding Nebula. Astronomy 723. P.A. Shaver: Active Galactic Nuclei in Abundances of Two New Extreme Met- and Astrophysics. Cosmology (A review of literature pub- al Poor Giants. Astronomy and As- lished from July 7987 to June 7990, for trophysics, Letters. 717. WW. Zeilinger et al.: NGC 5084: A Mas- sive Disc Galaxy with a Tilted Ring. M. N. R. A. S. 718. G. Zhao and P. Magain: The Chemical Composition of the Extreme Halo Stars. Ill. Equivalent Widths of 20 Dwarfs. As- tronomy and Astrophysics Suppl. Visiting Astronomers 719. A. F. M. Moorwood: lnfrared Capa- bilities of Very Large Groundbased Te- (October 1,1990-April 1,1991) lescopes. Invited paper presented at the COSPAR XXVlll Symposium "The Observing time has now been allocated for Sneden, Moehler/de Boer, Mazure et al. - 1- lnfrared and Submillimeter Universe at Period 46 (October 1, 1990-April 1, 1991). 01 4-43 K, Danziger/Bouchet/Lucy/Fransson/ High Redshifts". To be published in Ad- As usual, the demand for telescope time was Mazzali/Della Valle/Gouiffes, Turatto et al. - vances in Space Research (Pergamon, much greater than the time actually available. 4-004-45 K, de Lapparent et al. - 1-003-43 K, Oxford). The following list gives the names of the Shaver, Macchettoflurnshek, DanzigerIBou- 720. P. Crane et al.: The Interstellar 12c/13c visiting astronomers, by telescope and in chet/Lucy/Fransson/Mazzali/Della Vallel Ratio Toward y Normae. Astrophysical chronological order. The complete list, with Gouiffes, Turatto et al. - 4-004-45 K. dates, equipment and programme titles, is Journal. Nov. 1990: Mariotti/Cuby/Lacombe/LBna/ available from ESO-Garching. 721. M. Mariani and S.A. Bonometto: Ther- Merkle/Perrier/Rigaut, Gallais/Alloin/Rouan/ mal Evolution of Phases During the Lanq,on/LenalRigaut/Merkle, Combes M.1 Cosmological Quark-Hadron Tran- 3.6-m Telescope LenalRigaut/Merkle/Cuby/Tomasko/Saint- sition. Astrophysical Journal. Pe, Ogelman/Gouiffes/~elnick/~ugusteijn/ 722. A. Sandage and G.A. Tammann: Steps Oct. 1990: Danziger/Bouchet/Lucy/Frans- Hasinger/Pietsch/Pedersen, Ogelman/ Toward the Hubble Constant IX: The son/Mazzali/Della Valle/Gouiffes, Gratton/ Gouiffes, Danziger/Bouchet/Lucy/Fransson/

6 Mazzali/Della Valle/Gouiffes, Guzzo/Collins/ rego AlighierilTrinchieri/Sparks, FalomoTTan- S.R., Kohoutek, Hensberge et al. - 5-005- Nichol/Lumsden, Warren, Chambers, Mara- zinarenghi, Bender et al. - 1-004-45K, Ori- 45 K. no/Mignoli/Zamorani/Zitelli, Danziger et al. - glia/Brocato/Oliva. Feb. 1991: Loden L.O./Sundman, Gahm/ 6-003-45 K, Danziger/Bouchet/Lucy/Frans- March 1991: HainauVJarvis, Krautterl Loden K., Falomo/Maraschi/Tanzi~reves, son/Mazzali/Della Valle/Gouiffes, Simon/ Starrfield, Tarenghi/D'Odorico/Wampler/Pe- van Genderedvan der Hucht/Schwarz, Bian- Husfeld/KudritzkiNoels, KudritzkiNoels/ tersonNoshii/Silk, Bergeron et al. - 1-012- chini/Della ~alle/Ogelman/Orio/Bianchi. Husfeld/Gabler/Pauldrach/Puls, de Boer et 43K, Surdej et al. - 2-003-43K, Miley et al. - al. (Spite F.) - 3-003-43 K. March 1991: Gerbaldi et al. - 5-004-43K, 2-001 -43 K, Danziger/Bouchet/Lucy/Frans- The/de Winter/Bibo/Hu, The/de Winter/Hu, Dec. 1990: de Boer et al. (Spite F.) - 3-003- son/Mazzali/Della Valle/Gouiffes, Danziger/ Danziger et al. - 6-003-45 K, DurreVPetitjean, 43K, de Boer et al. (Molaro) - 3-003-43K, Moorwood/Oliva, Moorwood/Oliva. Reimers et al. - 2-009-45K, Danziger/Bou- Rifatto/Buson/Zeilinger, Rafanelli/Padrielli/ chet/Lucy/Fransson/Mazzali/DeIla Valle/ GregorinVMarziani, Courvoisier/Bouchet/Ble- Gouiffes, Soucail/Mathez/Mellier/Le Borgne, 2.2-m Telescope cha. Giraudlnfante, Turatto et al. - 4-004-45K, Oct. 1990: Goudfrooij/de Jong T./Joergen- Danziger/Bouchet/Lucy/Fransson/Mazzali/ sen H. E./Norgaard-Nielsen/Hansen, Barbieri 1.4-m CAT Della ValIe/Gouiffes, Meylan/Dubath/Mayor, et al. - 2-007-43K, Zeilinger/Buson/Gallettal Oct. 1990: Tagliaferri/Cutispoto/Giommi/ Dubath/Melnick/Mayor, de Boer et al. (Wolf) - Saglia, Turatto et al. - 4-004-45K, Zeilingerl Pallavicini/Pasquini, Char/Jankov/Foing/ 3-003-43 K. Buson/Galletta/Saglia, Barbieri et al. - 2-007- Neff/Fernandez/Rodono/Crivellari/Walter, 43K, Miley et al. - 2-001-43K, Test - Moor- Jan. 1991: Dougados/Rouan/LenalMerkle/ Tagliaferri/Cutispoto/Giommi/Pallavicini/ wood. Rigaut, Malbet/Bertout/Lena/Rigaut/Merkle/ Pasquini, Lagrange-Henri/Jaschek M./Ja- Cuby, Lena/Dougados/Merkle/Monin/Per- Nov. 1990: Test-Moorwood, van der KruiV schek C., Reimers/Toussaint/Hansen, Pas- rier/Rigaut/Ridgway, Ogelman/Gouiffes/Mel- de Jong R.S., Mirabel/Lagage/Cesarsky, de quini/Saar/Restaino, Gehren/Axer/Butler/ nic~Augusteijn/Hasinger/Pietsch/Pedersen, Boer et al. (Koornneef) - 3-003-43K, Dett- Fuhrmann/Steenbock/Reile. Ogelman/Gouiffes, Danziger/Bouchet/Lucy/ mar/Becker, Surdej et al. - 2-003-43 K, Berg- Nov. 1990: Gehren/Axer/Butler/Fuhrmann/ Fransson/Mazzali/Della Valle/Gouiffes, de vall/RonnbacWJohansson, Seggewiss/Fein- SteenbocklReile, Pols/WatersNerbunt/van Boer et al. (Azzopardi) - 3-003-43K, Beuer- steinNazquez, Christensen/Sommer-Larsenl Paradijs/Cote/v. KerkwijWvan den Heuvel, da mann/Trumper/Thomas/Reinsch/Simon, Hawkins/Flynn, Westerlund/Azzoppardi/Re- Silvdde la Reza, Vladilo/Centurion/Molaro/ Wampler et al. - 2-01 0-45 K, Schmutz/Nuss- beirot/Breysacher, Turatto et al. - 4-004- Monai, Maceroni/vanlt VeerNilhu, Char/Jan- baumerNogel, Hensberge et al. - 5-005- 45 K. 45 K, Foing/Collier-CameronNilhu/Gus- kov/Foing/Neff/Fernandez/Rodono/CrivelIari/ tafsson/Ehrenfreund. Dec. 1990: Chiosi/Ortolani/Bertelli/ Walter, Clausen, Char/Jankov/Foing/Neff/ BressanNallenari, Bhatia/Chiosi/Piotto/Pru- Feb. 1991: Danziger/Bouchet/Lucy/Frans- Fernandez/Rodono/Crivellari/Walter. gniel/MacGillivray, Chiosi/Ortolani/Bertelli/ son/Mazzali/Della Valle/Gouiffes, Turatto et BressanNallenari, de Boer et al. (Seggewiss) Dec. 1990: Char/Jankov/Foing/Neff/Fer- al. - 4-004-45 K, Reimers/Koester/Chan- 3-003-43 K, Dennefeld/Boulanger/Fru- nandez/Rodono/Crivellari/Walter, Fibre link - mugam, Danziger et al. - 6-003-45 K, Turatto - scione/Moshir, Polcaro/Giovannelli/Man- 3.6-m telescope, Lagrange-Henri/BeustNi- et al. - 4-004-45 K, Danziger/Bouchet/Lucy/ chanda/Norci/PollocWRossiNiotti, Wester- dal-Madjar/Ferlet, Benvenuti/Porceddu/Kre- Fransson/Mazzali/Della Valle/Gouiffes, Dan- Iund/Azzopardi/Rebeirot/Breysacher, de lowski, Cayrel de Strobel, Pols/WatersNer- ziger/Bouchet/Lucy/Fransson/Mazzali/Della Boer et al. (Wolf) - 3-003-43K, MPI time. bunthan Paradijs/Cote/van Kerkwijuvan den Valle/Gouiffes, Turatto et al. - 4-004-45K. Heuvel. Jan. 1991: MPI Time, Test-Moorwood March 1991: ZamoraniNettolani/Zucca/ Jan. 1991: Pols/WatersNerbunt/van Para- Scaramella/Chincarini/Burg, Bertola et al. - Feb. 1991: Danziger/Liu/Dalgarno, Bender dijs/Cote/van Kerkwijkhan den Heuvel, Kiirs- 1-008-43 K, Danziger/Bouchet/Lucy/Frans- et al. - 1-004-43 K, Sabbadin/CappelIaro/Tu- ter/Schmitt, Reimers/Toussaint/Hansen, son/Mazzali/Della Valle/Gouiffes, Danziger et ratto/Salvadori, Melnick/Bohringer/Giraud/ Nissen/Edvardsson, Boffin/Arnould/Abia/ al. - 6-003-45K, Bohringer/Seitter/Schueck- Voges/Peters/Zimmermann, Piotto/Capac- Isern/Forestini/Canal/Rebolo. er/Horstmann/Cruddace/Kowalski/Wallin/ cioli/Ortolani, Blommaert/Habing/v.d. Veen, PierreNoges/MacGillivray/Collins, Ogelman/ Groenewegedde Jong T./Hu. Feb. 1991: North, Char/Jankov/Foing/Neff/ Gouiffes/Melnick/Augusteijn/Hasinger/ FernandezlRodono/Crivellari/Walter, North, March 1991: Krautter/Ogelman/Starrfield/ Pietsch/Pedersen, Ogelman/~ouiffes, Dan- Char/Jankov/Foing/Neff/Fernandez/Rodono/ Williams, Tapia/Schwarz/Roth/Ruiz, van ziger/Bouchet/Lucy/Fransson/Mazzali/Della Crivellari/Walter, Grenon/Barbuy, Barbuy/ Haarlem/Katgert, Surdej et al. - 2-003-43K, Valle/Gouiffes, Perrier/Mariotti/Mayor/Du- MaededMedeiros, Sembach/Danks/Crane/ Miley et al. - 2-001 -43K, Danziger et al. - 6- quennoy. Savage, Reimers/Toussaint/Hansen. 003-45 K, Turatto et al. - 4-004-45 K, Danzi- ger/Moorwood/Oliva, SchwarzlMoneti. March 1991: Reimers/Toussaint/Hansen, 3.5-m NTT Hu, LanzlMathys/Gerbaldi/Faraggiana, Lanzl Mathys/Megessier/Landstreet, Waelkens/ Nov. 1990: Danziger/Bouchet/Lucy/Frans- 1.5-m Spectrographic Telescope van Winckel/Lamers/Trams, Boffin/Jorissen/ son/Mazzali/Della Valle/Gouiffes, Arp/Dan- Oct. 1990: Pallavicini/Tagliaferri/Gahm/ Groenewegen. ziger/Giraud, Fusi Pecci/Ferraro/Brocato/ Pasquini, Tagliaferri/Cutispoto/Giommi/Pal- Cacciari/Clementini/Buonanno/Zinn, Surdej lavicini/Pasquini, Kjaergaard Rasmussenl et al. - 2-003-43K, ElIis/Fosbury/Hook/CoI- 1-m Photometric Telescope Joergensen I., Barbieri et al. 2-007-43K, less/Broadhurst, Tarenghi/D'Odorico/Wam- - Dettmar/Koribalski/Krenz/Barteldrees, Oct. 1990: Tagliaferri/Cutispoto/Giommi/ pler/Peterson/Yoshii/Silk. Proust/Mazure/Capelato/Sodre, Renzinil Pallavicini/Pasquini, Fulchignoni/Barucci/De Dec. 1990: Butcher/van Rossum, Brocato/ Greggio/Bragaglia. Angelis/Burchi/Dotto/Ferrari/Foryta/Roques, Castellani/Ferraro, Giraud, de Boer et al. Cacciari/Clementini/Fernley, Pols~Watersl (Dennefeld) - 3-003-43K, Paresce/Clampin/ Nov. 1990: Gehren/Axer/Fuhrmann/Steen- Verbunt/van Paradijs/Cote/v. Kerkwijk/van Moneti/Golimowski/Nota, Lagrange-Henri/ bock/Reile, Paturel et al. - 1-017-45K, Dan- den Heuvel. ziger et al. - 6-003-45K, Jasniewiczflheve- MaillardNidal-Madjar/Ferlet/Beust. Nov. 1990: Pols/WatersNerkunt/van Para- nin, Reimers et al. - 2-009-45K. Jan. 1991: Lagrange-Henri/MaillardNidal- dijs/Cote/v. Kerkwijkhan den Heuvel, Pru- Madjar/Ferlet/Beust, Boisson/Joly/Moor- Dec. 1990: Bues/Pragal, Lub/de Ruiter, de gniel/Rampazzo/Combes F., Di Martinol wood/OlivaANard, Danziger/Bouchet/Lucy/ Ruiter/Gregorini/Parma/Vettolani, Calvani/ Mottola/Gonano/Neukum, Gieren/Moffett/ Fransson/Mazzali/Della Valle/Gouiffes, Gil- MarzianVAcosta, Courvoisier/Bouchet/Ble- Barnes, Bouvier/Martin E./Malbet/Menard/ mozzi/Blades/Madau, Bignami et al. - 6-002- cha, Gerbaldi et al. - 5-004-43K. FernandezlMatthews/Terranegra/Alcala. 45 K, Fort et al. - 1-015-45 K, Reipurth. Jan. 1991: Gerbaldi et al. - 5-004-43K, Dec. 1990: Bouvier/Martin E./Malbet/ Feb. 1991: Poetzel/Ray/Mundt, Della Valle/ SauvageoVRothenflug/Dubreuil/Ballet, Pa- Menard/Fernandez/Matthews/Terranegra/Al- CapaccioIi/Piotto/Wagner, Macchetto/di Se- kuII/Motch/Bianchi, Walsh/Walton/Pottasch cala, Liller/Alcaino/Alvarado/Wenderoth, Vi- dal-MadjadLagrange-Henri/Beust/Ferlet/ kvist/Hahn/Magnusson/de Campos/Cuy- Gouiffes/Lucy/Fransson/Mazzali/Della Valle, Foing/Char, Giard/Bernard/Dennefeld/Sales, pers/Cutispoto, ArlotTThuillot/DescampsNu/ Waelkens/Mayor, Mermilliod/Mayor. Le Bertre et al. - 5-006-45K, Arlot/Des- Colas, Debehogne/Di MartinoIZappalULa- March 1991: Mermilliod/Mayor, Danish camps/Thuillot/ColasNu, Le Bertre et al. - 5- gerkvist/Hahn/Magnusson/de Campos/Cuy- Time, Ardeberg/Lundstr6m/Lindgren, 006-45 K. pers/Cutispoto, ArlotTThuillot/DescampsNu/ Colas, Debehogne/Di Martino/Zappala/La- Jan. 1991: Le Bertre et al. - 5-006-45K, gerkvist/Hahn/Magnusson/de CamposICuy- Courvoisier/Bouchet/Blecha, Pols/Watersl pers1Cutispoto. 50-cm Danish Telescope Verbunt/van Paradijs/Cote/van Kerkwijkhan den Heuvel, Sterken/Longo/BusareIlo, ArloW March 1991: The/de Winter/Bibo/Hu, Arlotl Oct. 1990: Group for Long Term Photome- Descamps/Thuillot/ColasNu, Le Bertre et al. Thuillot/DescampsNu/Colas, The/de Winter/ try of Variables, Ardeberg/Lundstrom/Lind- - 5-006-45 K, Foing/ColIier-CameronNiIhul Bibo/Hu, Cutispoto/GiampapdPasquini/ gren, Group for Long Term Photometry of Gustafsson/Ehrenfreund, Le Bertre et al. - 5- LetoIPagano, Arlot/ThuiIlot/DescampsNu/ Variables. 006-45 K. Colas, Cutispoto/Giampapa/Pasquini/Leto/ Nov. 1990: Group for Long Term Photome- Pagano, Peres/Cutispoto/Reale/Serio/Leto/ Feb. 1991: Le Bertre et al. - 5-006-45K, try of Variables, Danish time, EinickeIFa- Pagano. Courvoisier/Bouchet/Blecha, Hoffmann/Gey- bricius/Helmer, Group for Long Term Photo- er, Groenewegedde Jong T./Hu, Arlot/Des- metry of Variables. camps/Thuillot/ColasNu, Lorenzetti/Molinari, GPO 40-cm Astrograph Dec. 1990: Group for Long Term Photome- Courvoisier/Bouchet/Blecha, The/de Winter/ try of Variables. Hu. Nov. 1990: Elst/Hoffmann/Shkodrov. Jan. 1991: Group for Long Term Photome- Dec. 1990: Vidal-Madjar. March 1991: The/de Winter/Hu, Robberto/ try of Variables, Danish time, Group for Long Busso/Guarnieri/Scaltriti/Silvestro/Persi, Feb. 1991: Munari/Lattanzi/Massone, Term Photometry of Variables. ManfroidNreux, Arlot/Descamps/Thuillot/ Massone. ColasNu, Catalano F.A./Leone/Kroll, Cour- Feb. 1991: Group for Long Term Photome- voisier/Bouchet/Blecha. March 1991: Debehogne/Machado/Caldei- try of Variables, Olsen, Maitzen/Leone/ raA/ieirdNetto/ZappalUde Sanctis/Lager- Catalano F.A./Jenkner. kvist/Mourao/Protitch-Benishek/Javanshir/ March 1991: Franco, Ardeberg/Lundstrom/ 50-cm ESO Photometric Telescope Wosczcy k. Lindgren, Catalano F.A./Leone/Kroll. Oct. 1990: Char/Jankov/Foing/Neff/Fer- nandez/Rodono/Crivellari/Walter, Surdej/De- 1.5-m Danish Telescope tal/Hainaut/Pospieszalska-Surdej, Catalano 90-cm Dutch Telescope F. A./Schneider H.1Leone. Oct. 1990: Ardeberg/Lundstrom/Lindgren, Caon/Capaccioli, Danziger/Bouchet/ Oct. 1990: van Genderen. Nov. 1990: Catalano F.A./Schneider H./ Gouiffes/Lucy/Fransson/Mazzali/Della Valle, Leone, Schober, Maceroni/vanlt VeerNilhu, Nov. 1990: van Genderen, Dutch time. Capaccioli/Bresolin/Ortolani/Piotto, Mazure Char/Jankov/Foing/NefflFernandez/Rodonol et al. - 1-014-43 K, Athanassoula/Bosmd Dec. 1990: Dutch time, van Genderen, Crivellari/Walter, Arlot/Thuillot/Descamps/ ButdCrocker, Saust, Andersen/Nordstrom/ Lub/de Ruiter. Vu/Colas, Char/Jankov/Foing/Neff/Fernan- Mayor/Olsen. dez/Rodono/CrivelIari/Walter. Jan. 1991: Dutch time. Nov. 1990: Danish time, Mayor et al. - 5- Dec. 1990: Char/Jankov/Foing/Neff/Fer- Feb. 1991: Ferrari/Bucciarelli/Massone/ 001-43 K. nandez/Rodono/Crivellari/Walter, Gocher- Koornneef/Lasker/Postman/Siciliano/Lattan- mann/Grothues, Mantegazza/Antonello/Po- Dec. 1990: Mayor et al. - 5-001 -43K, Lor- zi, van Genderenhan der Hucht/Schwarz. retti, Arlot/ThuiIlot/DescampsNu/Colas, tet/Lindgren/Martin N., Vio/Cristiani/Della March 1991: Dutch time. Mantegazza/Antonello/Poretti. Valle/La Franca, Danziger/Bouchet/Gouiffes/ LucylFransson/Mazzali/Della Valle, Surdej et Jan. 1991: Mantegazza/Antonello/Poretti, al. - 2-003-43K, QuintandRamirez, Vidal- Kohoutek, Arlot/Thuillot/DescampsNu/Co- SEST Madjar, Prugniel/Bhatia/McGiIlivray/Piotto, las, Kohoutek, Arlot/Thuillot/DescampsNu/ Danziger/Bouchet/Gouiffes/Lucy/Fransson/ Nov. 1990: Chini, Casoli, Bresolin, Com- Colas, Kohoutek, Schmutz/Nussbaumer/ Mazzali/Della Valle, Danish time. bes, Becker, Kazes, Dettmar. Vogel, Arlot/ThuiIlot/DescampsNu/Colas, Schmutz/NussbaumerNogel, Foing/Collier- Jan. 1991: Danish time, Mayor et al. - 5- Jan. 1991: Wielebinski, Loiseau, Oosterloo, CameronNiIhu/Gustafsson/Ehrenfreund. 001 -43 K. Huchtmeier, Dennefeld, Wild/Eckart, van der Hulst, Israel, Rothermel, de Graauw, Israel. Feb. 1991: Foing/Collier-CameronNilhu/ Feb. 1991: Mayor et al. - 5-001-43K, Gustafsson/Ehrenfreund, Char/Jankov/ Gahm/Loden K., West, Bender et al. - 1-004- March 1991:Tacconi, Beckman, Cameron, Foing/Neff/Fernandez/Rodono/CrivelIari/Wa- 43 K, Caon/Capaccioli/Ferrario, Groenewe- Gerin, Wild, Cox, Lequeux, Cox, Stark, Hen- Iter, Debehogne/Di Martino/ZappalB/Lager- gen/de Jong T./Hu, Danziger/Bouchet/ kel, Arnal, Groenewegen, Hu, Foing.

During 2nd ESOIOHP Summer School in Astrophysical Observations: Observatoire de Haute-Provence Becomes a European Northern Observatory M. VERON-CETY, Observatoire de Haute-Provence, C. N. R. S., France D. BAADE, ESO

There is a strong trend towards an ness of its site. There are good reasons the usage of up-to-date instruments and ever tighter correlation between the for this. But it has the negative side the handling of the data they provide. quality of the equipment of an as- effect that students find it more and This simple recognition led the Euro- tronomical observatory and the remote- more difficult to get adequate training in pean Southern Observatory and the Ob- Figure 1: General view of OHP: in front are the workshops and administrative buildings. The two biggest telescopes are the 1.93 m and 1.52 m telescope.

servatoire de Haute-Provence (OHP) to the Summer School, the OHP had set high-resolution spectrograph AURELIE, organize a first joint Summer School in aside three nights at the 1.93-m tele- and 6 nights for direct imaging with the Astrophysical Observations which was scope for low-resolution spectroscopy 1.20-m telescope. All three instruments held in July 1988 at OHP (see the report with the CARELEC spectrograph, three are equipped with CCD detectors. Three by A. Chalabaev and S. D'Odorico in the nights at the 1.52-m telescope with its groups observed with the 1.93-m and Messenger No. 53, p. 11). Since all involved felt that this first experiment was very successful, it was List of courses: decided that now, 2 years later, organiz- R. Wilson (ESO): Modern telescope layout ing a second Summer School was very M. Dennefeld (IAP, Paris): High-sensitivity detectors timely. In fact, the number of more than J. Wampler (ESO): High-throughput optical instruments 50 applications convincingly confirmed F. Rufener (Geneva): Photo-electric photometry this view. Unfortunately, the capacity of S. llovaisky (OHP): Photometry with CCDs D. Gillet (OHP): High-resolution spectroscopy the facilities of OHP and the intended F. Merkle (ESO): High-resolution imaging character of the Summer School limited C. Vanderiest (Meudon): Low-resolution and multi-channel spectroscopy the number of participants to eighteen. F. Sibille (Lyon): Infrared observations The selection process was, therefore, a D. Baade (ESO): lntroduction to MlDAS very difficult one because we could M. Veron (OHP): Introduction to IHAP accept only a fraction of the candidates Tutoring astronomers: D. Baade (ESO), E. Brocato (ESO), M. Dennefeld (IAP), D. Gille which we should have liked to invite. (OHP), S. llovaisky (OHP) and P. Veron (OHP). All participants arrived at OHP in the Students: J.-L. Beuzit (ESO), N. Caon (Padova, Italy), M. Cassiano (Gottingen, Germany), P morning of July 16. After lunch, they met Cruzalebes (Nice, France), R. den Hartog (Leiden, the Netherlands), J. Eisloffel (Heidelberg to form six teams of three students and Germany), F. Guglielmo (Meudon, France), F. G. Jensen (Arhus, Denmark), L. Kaper (Amster. one tutor each (their names are given in dam, the Netherlands), A. Klotz ~oulouse,France), A. Lan~on(Paris, France), X. Liu (ESO), J the separate box accompanying this ar- Meijer (Munster, Germany), 0. Moreau (Paris, France), C. Pichon (Meudon), France), A ticle) and to plan and prepare the work Smette (ESO), M. Vestergaard (Copenhagen, Denmark), T. Zwitter (Trieste, Italy). to be done during the next ten days. For days at OHP for in-depth discussions. Indisputable highlight was a joint, un- scheduled presentation by Joe Wampler and Ray Wilson (both from ESO) which they had offered in order to bring the students up to date on the symptoms and interpretation of the optical anomalies of the Hubble Space Tele- scope. The programme was rounded of by a visit of Ray Wilson to one of the tele- scopes where he explained what can be inferred about the aberrations of a tele- scope from the image of its pupil. Final- ly, through the kind invitation of Prof. Michel Mayor of the Observatoire de Geneve, the students had the opportu- nity to complement their experience with modern instruments by watching CORAVEL being used at the Swiss 1-m Figure 2: A group of students (A. Lan~on,N. Caon and J. Eisloffel) reducing CCD direct images telescope. at the /HAP station of the 1.20-m telescope. In many of the applications received for the Summer School, a strong interest was expressed in working with col- leagues from other countries in an inter- the other three with the 1.52-m tele- ture data, and eventually put into the national environment. With nearly a scope for one night each whereas all form of scientifically meaningful and es- dozen different nationalities, this desire groups had one night at the 1.20-m tele- thetically pleasing viewgraphs. In this was well satisfied. So, at least for the scope. With only minor exceptions, the way, the students were exposed to a duration of the Summer School, one weather cooperated during all nights. fairly broad range of applications soft- could speak of the OHP as a European The observing programmes had ware in MlDAS as well as IHAP. Northern Observatory. The enthusiasm mostly been worked out by the group The only major break was on Sunday, and good spirit of the students, the un- tutors but in some cases also included July 22, when an excursion to the near- tiring efforts of the tutors, the helpful- proposals made by the students. The by town of Forcalquier and its citadelle ness of numerous OHP technical staff, targets ranged from IRAS galaxies over and a picnic close to the old monastery and the skill of the lecturers in explaining open star clusters to fi Cephei stars, of Ganagobie provided a welcome complex subjects made this Summer close X-ray binaries, OB supergiants, opportunity to rest for a while. School a very rewarding experience for and FU Ori stars. The scientific subjects On the last day, July 26, each group the organizers. We cordially thank them helped to provide a realistic background presented their work and results in a all. to the practical work done. But the main short talk of about 20 minutes duration emphasis was on the latter: How does to the other participants. Although one select targets? Where do coor- rumours had it that some groups hardly dinates and finding charts come from? saw their beds in the preceding night, What other information is needed at the the presentations made were without The following ESO Workshop Proceed- telescope? How does one estimate ex- exception of a very high standard and ings will become available in October posure times? What calibration sources well reflected the intense learning pro- 1990: cess of the past ten days. are available; which ones are required 2nd ESOIST-ECF for a given programme? How many dif- Since OHP could provide state-of- ferent instrument set-ups can I handle in the-art instruments with modern com- Data Analysis Workshop one night? In short, all the do's and puter-based user interfaces plus both The price of this 150-page volume, don'ts of astronomical observations on MlDAS and IHAP for data reduction, edited by D. Baade and P.J. Grosberl, is which standard text books but also every student should now be in a good DM 20.- (including packing and surface mail). many user guides quit. Most pro- position to conduct observing pro- grammes were on purpose not very am- grammes at La Silla or elsewhere on his1 Bulges of Galaxies bitious in order to leave sufficient room her own. This we had defined as the for (minor) errors which so often are the primary scope of the Summer School. The Proceedings of this first ESO/CTIO Workshop, edited by B.J. Jarvis and most efficient teachers. As stated above, the tutors guided D.M. Terndrup, contains 376 pages and and supervised the work of their respec- One of the lessons which every stu- is offered at a price of DM 40.- (including dent learned (and even some of the tive groups. But there should also be a packing and surface mail). tutors were reminded of it) is that the more systematic introduction to the Payments have to be made to the ESO time required for the proper reduction of physical basis and the practical design bank account 2 102 002 with Commerz- data exceeds the time for their acquisi- and operating principles of the types of bank Munchen or by cheque, addressed tion by a large factor. The students re- facilities the students were using. This to the attention of sponded to this challenge with consid- was provided by a series of eleven one- ESO, Financial Services erable diligence. All computers were and-a-half hour lectures which were giv- Karl-Schwarzschild-StraBe 2 given a hard time, often nearly round the en by various renowned experts (see D-8046 Garching bei Munchen. Please do not forget to indicate your box). The students interacted with the clock. The observations were tested for complete address and the title of the Pro- instrumental defects, calibrated and speakers in lively conversations, and ceedings. counter-checked, compared to litera- most lecturers kindly spent some extra Selection of the VLT

The readers of the Messenger may the ESO Council passed the following ESO Committees and Council later this wonder how the selection of the site for resolution: "Council, taking note of the year. the Very Large Telescope (VLT) is pro- superior scientific qualities of the Para- In this connection, a completely inde- ceeding. The interest in this important nal area, asks the ESO Executive to pendent line of approach to the ques- matter seems to be rising; hardly a day work out financial, technical and re- tion of the long-term climatic stability in passes without a corresponding request search policy implications and opera- Northern Chile has become available. for information to the ESO Information tional models of ESO/Chile for the Para- Dr. Michel Grenon of the Geneva Obser- Service. nal area option as well as for the Viz- vatory, a regular visiting astronomer to Here is a short summary of the current cachas option." La Silla during the past two decades situation. This work is now under way at ESO. and a botanist with strong interests in The Site Selection Working Group At the same time, a modified Site Selec- biogeography, has recently submitted a (SSWG phase I: Chairman J.-P. Swings) tion Working Group has taken up its report on the climate in and around the delivered its final report about the work during a first meeting at the ESO Atacama desert, as deduced from sour- meteorological conditions in the Paranal Headquarters on July 25. Whereas in ces, not considered in the SSWG study, and La Silla areas in early May this year. the first phase, the SSWG mainly looked but indicative of the climatic conditions This report was thoroughly discussed into the scientific aspects of the site in the past and the present around the by the Scientific Technical Committee choice, the terms of reference for SSWG possible VLT sites. (STC) during its meeting on May 10-1 1. phase II, as defined already in De- We are very pleased that Dr. Grenon The STC passed a resolution, which en- cember 1988, also include the opera- has agreed to the publication of a popu- dorsed the SSWG I recommendation to tional and financial pros and cons of the lar account of this most interesting establish the VLT Observatory in the site options. J.-P. Swings (Belgium) biogeographical study in this issue of Paranal area and recommended that the continues as Chairman; other members the Messenger. We warmly commend it ESO Executive work out and present a are I. Appenzeller (F.R. Germany), A. to the attention of our readers. viable operational model of ESO/Chile Ardeberg (Sweden), G. Lelievre (France) In accordance with the original plan- with the Observatory on La Silla and and S. Ortolani (Italy). ning, it is hoped that it will be possible to the VLT Observatory in the Paranal The SSWG II will have the impor- decide about the future VLT site before area to the STC, the Finance Commit- tant function of providing guidelines for the end of the current year. In that case, tee and Council in November/Decem- and running criticism of the in-house the ground preparation (blasting, etc.) ber 1990. study by the ESO management, before will start on-schedule in early 1991. In its meeting in Sweden on June 7, it is finalized and presented to the The Editor

The Northern Chile Climate and Its Evolution A Pluridisciplinary Approach to the VLT Site Selection M. GRENON, Geneva Observatory, Switzerland

1. Introduction Several factors complicate the selec- and possibly meaningless unless it is The selection of an optimum as- tion of the site. A major problem is the synchronous. With a semi-periodicity of tronomical site in northern Chile, under- scarcity of meteorological stations in 8 to 12 years, cf. section 3, measure- taken by ESO for several years now, is a northern Chile, as they are mainly lo- ments over 30 to 40 years are necessary very complex task. The location of the cated along the coast, below the inver- to characterize the local mean climatic VLT will effect the efficiency of the Euro- sion layer, or distributed in the main conditions. pean astronomical community for the valleys. Little is known about the An- The aim of this report is to provide next 30 to 50 years. Therefore, it is of dean or the precordillera area climate, information on the existing and antici- prime importance that the selected site south of 23 "S. The rather short dura- pated sites, complementary to that col- optimizes the quality and the quantity of tion of continuous records of half a cen- lected by ESO investigators during the the collected data for the whole range of tury or less, depending on the measured site testing campaign. wavelengths being of interest now and quantities, make the definition of mean The present approach utilizes in the future. At least four different para- meteorological values and trends uncer- biogeography as a tool to define with a meters have to be considered: tain. Another important problem is the high spatial resolution the integrated 1. the quality of the images (seeing); vastness of the domain to be investi- climatic properties over various time 2. the quality of the atmospheric trans- gated, i.e. about 1000 km in latitude and scales depending on the life duration parency, namely the amount of 200 km in longitude in which the poten- and propagation times of living beings aerosols and of the precipitable wa- tial sites are located in non-populated considered. The data used here are ter and their time variation; areas and hence have no meteorologi- either compiled from specialized litera- 3. the annual distribution of photomet- cal or historical records. In the southern ture or are the results of mainly botani- ric and spectroscopic nights; part of the Atacama desert, the occur- cal observations, made by the author in 4. the intermediate and long term rence of quasi periodic wet episodes Chile since 1971. The connection with evolution of climate with local re- separated by series of dry years, makes meteorological and climatical parame- sponse to global climatic changes. the comparison between sites difficult ters will be made in order to define the astronomical properties of northern running warm current. During the lower mm 200. ', Chile sites, in comparison with Cerro Pliocene, the Atacama climate remained Tololo and La Silla sites. warm but not arid. It is only from the 180- ; The sensitivity of local conditions to lower Pleistocene on, during glacial and small and large amplitude climatic interglacial episodes, that the colder changes will be explored, using data humid periods started to alternate with from the fields of palaeobotany, glaciol- warm and dry ones. The aridity was ogy, and geology. intensified at each interglacial period as a result of the height increase of the Desaguadero Andes through intense andestic activity 2. The Origin of the Atacama Desert (Arroyo et al. 1988). The present day extreme arid condition was reached The Atacama desert is, geologically only at the end of the Pleistocene about speaking, a rather young feature. Its de- 10,000 years ago. velopment started during the Miocene, Nowadays, the wet continental tropi- about 12 Myr ago, when the uplifting of cal air masses are stopped east of the the Andes Central Cordillera pro- Andes and may cross the Andes only in gressively interrupted the zonal circula- southern summer, during the so-called tion at low altitudes. Erosion and canyon Bolivian winter, when the Pacific anti- cutting on the western flank ceased at cyclone is moving southwards, cf. Fuen- the Miocene-Pliocene boundary, about zalida (1983). But even if saturated when 5.3 Myr ago, as a consequence of the crossing the Andes, the adiabatic warm- intensification of the Humboldt current, ing of the air by 10 to 30 degrees leads Figure 2: The annual distribution of precipita- and of the regression of the counter- to a relative humidity of less than 30% tions at different sites close to the Chilean- at low altitudes. Peruvian border east of the main Cordillera On the western side, the Pacific anti- (Rodriguez, 1988). Measurements of annual cyclone prevents the penetration of po- rain precipitation show that precipitations in- lar air masses over the continent at duced by easterlies are regular, cf. Figure 3, latitudes approximately north of 25 "S. and allow the development of a rich flora and The presence of cold waters of the fauna. An increase of moisture in the atmo- Humbolt current at tropical latitudes in- sphere in northern Chile is to be expected duces temperature inversion at an al- from December to March. titude of 900 m near La Serena to from 1500 m east of Arica to 3000 m 1300-1 500 m between Taltal and An- east of Antofagasta. tofagasta. This inversion, with its The northern part is a cold air and rain associated quasi-permanent sea of shadow desert with a climate deter- clouds, inhibits the sea evaporation as mined by the yearly latitudinal oscillation well as the vertical atmospheric turbu- of the intertropical convergence. The lence. The Pacific humid air masses pluviosity shows a steep increase to- penetrate into the continent only when wards the east. Up to 4000 m, regular the coastal Cordillera is depressed, or precipitation as rainfall occurs between through the main valleys, pumped by November and April with annual maxima local thermal winds. reaching 300 mm to 400 mm at the Boli- Between the latitudes 19"30 S and vian border, see Figures 2 and 3. 25 "S there is no significant discon- South of 24-25 "S the precipitations tinuity in the western mountain range are due to the polar front activity bring- and so, for about 600 km, the Pacific air ing moisture from the south-west. Here, mass is completely blocked over the between April and September, the rise sea and the narrow coastal strip. As a of cool moist air produces condensation consequence, one of the most arid de- as rainfall or, if above 3000 m, as snow- serts of the Earth was able to develop fall over the precordilleras and cor- over the coastal Cordillera and in the dilleras. central depression. In stable conditions, the atmospheric transparency corre- The occurrence of fronts is controlled sponds to the properties of a modified by the latitudinal yearly oscillation of the tropical maritime air mass, dry and with South Pacific anticyclone centred at a low aerosol content. about 27 "S in winter and 30 "S in Figure 1: The distribution of the mean annual summer. The virga phenomenon, i.e. precipitation over northern Chile in units of the evaporation of rain drops in low al- mm H20. The cross indicates the site of 3. The Climate of Atacama Paranal (Huber, 1979). The nucleus of the titude dry air layers, is frequent. That is Atacama desert, i. e. the orographic depres- Although arid climate prevails from why rain over the central depression and sion between 19 " and 25 "S is the most 15 "S to 28 "S in Chile, the climatic the coastal mountains is so scarce and arid desert of the Earth with annual precipita- conditions are distinct in the northern, irregular. The warm tropical desert ends tion as low as 3.1 mm at Pintados (20'27 S, eastern and southern borders of the de- at latitude 27 "S, about 50 km north of 69'29 N) and a daily amplitude of the tem- sert. The extension of the extreme arid Copiapo. perature exceeding 25 "C during more than conditions, defined by precipitation less 9 months per year (Weischet, 1966). Along 4. The Transition Zone the northern coast, precipitation is even less, than 10 mmly, may be seen in Figure 1. e. g. 0.6 mm at Arica or 2.2 mm at Antofagas- The limits of absolute desert are narrow- The transition zone is of particular in- ta, but the relative humidity is high. er, with a maximum altitude ranging terest since it contains the three major when fronts normally produce not rain but only cloudiness at La Silla. The dot- ted area in Figure 5 is indicative of the number of hours which could be gained by moving the observatory to the North. Between the Elqui and Copiapo val- leys, winter precipitation is highly irregu- lar and, north of Vallenar, totally dry years may occur. The total annual precipitation Figure 5: The monthly number of lost photo- at La Serena (lat. 2954 S), Vallenar (lat. metric hours during non-photometric nights 28'34 S) and Copiapo (lat. 27'20 S), for the period 1966 to 1972 at La Silla. for the years 1970-1 984, are shown in Figure 6. The decrease of the precipita- tion, over these 250 km only, is as spec- conditions prevailing at Cerro Tololo, tacular as the increase of the variability show similar patterns but with more pro- 01 from year to year. nounced and frequent secondary 1933 1940 ' 1950 1960 1967 In order to study the intermediate time Figure 3: Annual precipitation at Parinacota peaks. The regularity of rainy years is station, latitude 18"12, longitude 6g020 W scale climatic variations, longer series increasing towards the South whereas and altitude 4360 m. Notice the limited range have to be considered. In the absence in the intermediate zone there appears of year-to-year variation. Adapted from of a dense net of nivo- and pluviometers to be a quasi biblical alternance of rich Niemeyer (1 968). in the transition zone, the mean flux of and poor harvests. the major rivers and their affluents are When compared during dry years, the used as indicators of the mean precipi- mountain sites between Elqui and astronomical sites now operating in tations in their basin. Fluxes are moni- Copiapo valleys would show little differ- Chile. It is also the zone where the tored in the area since 1942 and the ence in their quality as astronomical biogeography allows a very detailed most relevant data are the hydrograms sites. This may be the reason why La analysis of the past and present climatic of Rio Huasco and of its affluent Rio Silla mountain was selected after a conditions. Since it is a comparison Carmen alimented by precipitation fallen series of tests performed in that area zone for the northern sites of Paranal just east of La Silla, see Figure 7. during the dry years 1961-1962. In Fig- and Armazoni, its properties will be The most evident pattern is the re- ure 7, the peak in 1965 also explains more extensively described. currence of wet episodes with a semi- why the first measurements at La Silla This zone, between 27 "S and regular periodicity. Severe winters occur that year were somewhat disappointing. 34 "S, has a typical Mediterranean cli- every 7 to 12 years followed by pro- The transition zone is indeed the most mate characterized by sporadic winter gressive return to dry conditions. The sensitive to climatic changes and con- rains occurring when the anticyclonic flux distribution is somewhat smoothed sequently the southern limit of the conditions are briefly interrupted by by the delay between snowfall and melt- Atacama desert is expected to vary by short-lived cyclons, and followed by a ing at high altitudes about four months several hundred kilometres. dry summer and autumn. The amount of later, and by the low velocity of under- precipitation, as well as the duration of ground water. The volume of water 5. The Biogeography as a Site the wet season, steeply declines when measured in El Carmen correlates very Testing Tool moving to the north, see Figure 4 from well with the amount of precipitation Caviedes (1990). The number of cy- observed in the Vallenar area. Neverthe- The distribution of living beings, in clonic transits also declines towards the less, flux measurement appears to be a particular that of plants, is the result of North. At the latitude of La Serena, there better indicator of the winter severity at geological, biological and climatic are about 3 to 4 bad weather episodes Las Campanas and La Silla than the evolution. Various time scales are in- with a marked variability in intensity and pluviosity at Vallenar since it is not volved, from several million years for the number per winter. affected by the virga effect and thus families and genera differentiation, few At La Silla, the frontal activity is the represents the true frontal cloudiness thousand years for major climatic cause of a serious degradation of the over La Silla. changes to one year for blossoming of observing conditions in winter and The hydrograms of Elqui, Hurtado and annuals. spring. The highest percentage of non- Limari rivers, characteristic of the winter At the present time the observed dis- photometric nights also occurs when tribution of plants, insects, reptiles, etc., the nights are the longest, it is therefore has almost reached a new equilibrium more realistic to consider the monthly after major changes of the last ice age. number of lost hours of observation. In Living species develop in well-defined Figure 5 we give the total number of biotopes. Plants in particular are hours lost during non-photometric adapted to more or less restricted nights at La Silla for the period ranges of temperature, total amount of 1966-1 972 which includes only one wet precipitation, soil acidity, insolation and episode, see Figure 7. In Figure 5, lost hygrometry. In the semi-arid and arid hours during partially photometric zones plants are characterized by their nights, i.e. with at least 6 hours of ob- capability to absorb water, to store it for servation, are not taken into account. the dry months or years and to resist Thus, Figure 5 gives only the lower desiccation. This desiccation, due to limits of lost observing hours. Monthly low relative humidity, effect of the solar JFMAMJJASOND precipitation in central Chile and loss of radiation and that of surface evapora- observing hours show a clear correla- Figure 4: Monthly precipitation at different tion reinforced by wind, is the limiting tion, see Figures 4 and 5, for the greater coastal stations of central Chile, from factor of major importance for the veg- part of the year, except for spring months Caviedes (1990). etal development. La Serena Vallenar humidity, so no special adaptation is 1 I required by plants to survive longer than one dry summer. The lower part of Elqui Valley, including Cerro Tololo Observa- tory, belongs to that climatic zone. The upper Elqui Valley is drier because of rain shadow produced by the precordil- lera and evapotranspiration due to strong thermal valley winds. Along the coast, the presence of cold humid Pacific air and fog allows the development of a peculiar floristic association including bromeliaceae and cactaceae. The transition between the Mediterra- nean and semi-arid zone occurs north of La Serena, and is completed at Cuesta de Buenos Aires. From there to the Figure 6: The total annual rain precipitation at La Serena, Vallenar and Copiapo, between 1970 north of Copiapo, the winter watering is and 1984. no longer guaranteed and species have to survive, as seeds or bulbs, succulents Plants or plant associations with well- associate to each vegetal group a set of or other forms, through one to several defined climatic requirements may be climatological parameters. They are de- dry years. In this area, several cac- used to map the areas where the clima- termined by interpolating meteorologi- taceae develop relatively enormous tic conditions are within the permitted cal data collected in the considered underground water reservoirs, like those range for a given species or group. In area, if existing, and in adjacent areas. of Opuntia archiconoides, a local en- semi-arid zones, although the plant den- The preselection of astronomical sites, demic of Vallenar Cordillera, found at La sity is small, botanical surveys may re- worthy of testing, can indeed be made. Silla, see Figure 8. veal microclimates with a resolution as In the semi-arid zone, when the In the alluvial plains, at intermediate high as a few metres. ground coverage is high enough, the altitude, where the soil is deep enough Life cycles are very distinct from location of the domes on a given site to retain humidity, a few times per de- species to species. Annuals, with seeds may be optimized by using the distribu- cade, irregular rainy winters produce a easily dispersed by wind, are tracers of tion of plants with distinct sensitivity to spectacular blossoming desert. The typ- the short time climatic conditions. Pe- the winds, thermal or dominant. ical vegetal association producing this rennials are indicative of mean condi- phenomenon extends from Cuesta de tions over few vears to a centurv or Buenos Aires to few pockets, about more, depending on their life time and 6mThe Phytogeographic Zones 50 km north of Copiapo (see map in the time to reach maturitv., S~ecies.. Figure 9). This is the zone where polar adapted to restricted climatic conditions Phytogeography reveals a clear zona- front activity produces at least 20 mm of and with little efficiency in seed disper- tion in latitude and altitude south of precipitation semi-regularily. In this sion, are tracers of long term conditions. 26 "S. From Elqui Valley to the San- zone, tree cactaceae are confined to This is the case with most of the Chilean tiago area, a Mediterranean vegetation places invaded by fog during the night. cactaceae. prevails with rare trees, perennial In comparison, similar species are found Plant distribution, i.e. phytogeogra- bushes, tree cacti and a rich flora of close to the summit of Cerro Tololo. phy, allows to define the climatic condi- herbs in blossom at the end of winter. North of 26 "S parallel, the zonation tions over very extended areas, and to Winter watering is regular as well as becomes East-West. A strip along the

Figure 8: The root system of Opuntia ar- Figure 7: The hydrogram of Huasco river (upper curve) and (in black) that of Rio Carmen as chiconoides, a La Silla plant adapted to long measured at San Felix, latitude 28'56 S. From Direccion General de Aguas. duration droughts. From Hoffmann (1989). 14 coast, narrowing towards the equator, from the coast. This is an evidence that, hosts extremely specialized vegetal at that latitude, coastal summits are cer- associations, which in general are able tainly astronomically better than interior to retain water from fog only. In fog ones. pockets like Paposo, north of Taltal, ex- tremely distinct associations are found. 7. Other Biological Evidences The high rate of endemics indicates that these local climatic conditions are in- Animals through their food resources deed very ancient. Between Taltal and can also be used as climatic tracers. As Antofagasta, above the inversion layer, an example, in Figure 10, we give the i.e. above about 1300 m, warm desertic distribution of reptiles belonging to conditions prevail, with none to very lguanidae and Colubridae families. The scarce vegetation. On the western Cor- number of reptile species is limited, not dillera, the vegetation is essentially inex- only by the availability of their prey, as istent below 3000 m. At Paranal, only insects, and hence of vegetation, but one perennial was found in January also by temperature. The density of 1990, and at Armazoni, two species species is 10 to 12 species at maximum adapted to extreme conditions have between 33 "S to 35 "S, and also been collected. These are a succulent shows a relative maximum in the central plant, Philippiamra pachyphylla, and a depression. The density remains con- visquous one, Adesmia atacamensis, stant at 5-6 between Coquimbo and which is also found on other summits in Copiapo and falls to 1 or 0 north of the area. At Armazoni, their presence, as 26 "S. well as erosion features near the top, The only area without reptiles of these indicate that watering indeed occurs in families on the western Cordillera is be- the area with some regularity. Hoar frost tween 24"20 S and about 26'1 5 S. In or even snow may be expected at Arma- the central Andes, the density is small zoni. According to Figure 9, the abso- and falls to about 0 at 24 "S, but shows Figure 10: Density of reptile species belong- lute desert stops 80 to 110 km east from a sharp increase east of Calama where ing to lguanidae and Colubridae families, the coast, followed by a tropical semi- the altiplanic humidity is high because of mapped according to Donoso-Barros (1966) desert and at higher altitude by an An- Bolivian winter. species distribution. dean steppe. At the latitude of Paranal, the semi-desert starts at only 30 km 8. Phytogeographicallythe Optimum Latitude then be that which optimizes the yearly When moving towards the North, the distribution of observing time, i.e. by winter conditions improve continuously minimizing winter and summer losses. at least up to 27 "S. At some latitude, In the absence of a sufficient number the gain in observing time in winter will of Andean meteorological stations be- be compensated by losses during Boli- tween 22 "S and 28"S, the informa- vian "winter" in summer. Bolivian winter tion can again be deduced from phy- is expected to bring moisture in the at- togeography. Arroyo et al. (1988), have mosphere over the whole northern made six transects through the Andes Atacama desert, and for IR and millimet- between 18 "S and 29 "S, and have ric astronomy, its influence should be evaluated the richness of species as a minimized. The optimum latitude should function of the altitude and latitude. The temperature is merely indepen- dent on latitude and the richness is C essentially controlled by hygrometry. At Warm desert with scarce or no vegetation 26 "S, the richness is independent on I Tropical semi-desert altitude up to 4000 m. Closer to the Equator, the maximum species density Open subandean steppe with scrubs is found in the altitude range 3 Andean vegetation without succulents 3000-3500 m, and at lower altitudes south of 26 ". _] Andean steppe La Silla mountain with its estimated Coastal subdesertic vegetation richness of 130 species, according to ) Garrigue with evergreen bushes the author's collection, is just normal for its altitude and latitude with respect to I/] Desertic steppe with spring hygrophytes other Andean sites. 1 Semi-desertic steppe Figure 11 shows the total richness (N,,,) per transect and also at an altitude Subdesertic garrigue with succulents of 2500 m (N2500)as a function of the Coastal steppe with herbs and bushes latitude. North of 24 "S, richness is due to summer precipitation whereas south Salteddesert / 1 I of 26 "S to winter precipitation. By ex- F~gure9: Map of phytogeographic zones ln central and northern Ch~le(adapted from Geo- trapolating the curves for richness ver- graphla de Chile 111, Perez (1983) The sites of Paranal (I), Las Campanas (Z), La Sllla (3) and sus latitude for both regimes, we can Cerro Tololo (4) are Indicated by crosses. deduce that Bolivian winter contributes conditions at Paranal in the case of a ------. .* moderate greenhouse effect. ------The trends in the case of a global winter snow or rain planetary cooling are better docu- mented. The changes of snowline, of altiplanic lake shores (now salares), the fossil pollen records in peat bogs, and in particular the presence of relictual floras, belonging to Valdivian type rain forest at the Rio Limari latitude - the Fray Jorge and Talinay woods -, are all convergent indications of an important change of the southern and eastern limits of the Atacama desert. During the last ice age, the latitudinal shift of the vegetation was about 800 km. At that time, the conditions ex- isting now at La Silla were experienced close to Paranal, and those of Concep- cion at La Serena. Multiregressive models by Caviedes (1990) predict the amount of precipita- 180 19 20 21 22 23 24 25 26 27 28 290 tion and the change of snowlinefortem- perature falls. With respect to the pres- Figure 11 : The dependence of the plant diversity in the Andes, integrated along a transect N,, ent amount of rain, mm at La Sere- and at altitude 2500 m (N2500)as a function of latitude, adapted from Arroyo et a/. (1988) with an 117 estimate of Bolivian (summer rain) and Chilean winter extensions. na, a cooling by 1 ", 2 ", 3 "C would produce precipitation of 480, 967 and 1450 mm; resbectively. Thus, the zone at latitude 29 "-30 "S appears to be to plant diversity down to 27 "S, where- Palaeoclimatology indicates little highly sensitive to climatic changes as Chilean winter is perceptible up to change in temperature and humidity af- where a temperature drop of just 1 ", 24 "S. Thus, the optimum latitude for ter the end of Pleistocene, 11,400 years induces a precipitation increase by a an astronomical site is somewhere be- B. P.; isotopic datation of underground factor of four. tween 24'30 S and 25 "S. Paranal site water in the Antofagasta area confirms at latitude 24"37 S, is indeed perfectly the palynological findings, with an age 10. Conclusions located. of 10,000 years for this fossil water. During the moderate climatic op- In summary, the La Silla Observatory timum following the glacial period, i.e. is located in a transition zone visited by 9. The Long Term Climatic between 7300 and 3600 years B. P., the polar fronts which are responsible for a Variations temperature in the Andes was higher by serious degradation of winter observing In the southern Atacama desert, as 0.6 to 1.2 "C depending on the altitude. conditions. stated before, we observe intermediate The corresponding climates on the The weather conditions are variable time scale variations of climatic condi- western side of the Andes were recon- and semi-regular with time-scales in the tions with a quasi-periodicity of 7 to 12 structed by Lauer (1 986). order of a decade. Although an intensifi- years. There is some evidence for an The temperature rise led to an impor- cation of the aridity is noticed during the intensification of aridity during the past tant regression of the northern limit of last 50 years, the mean conditions 50 years, partly due to anthropic activi- the desert, from about 2 " to 8 "S, but appear to be stable over several cen- ty, but more so to real climatic change. had no noticeable effect on the southern turies. This zone is highly sensitive to At La Silla, the local endemic compo- limit at about 2V20 S, see Figure 12. global climatic changes where a tem- nent of the flora seems to be stable, This finding supports the stability of the perature drop of 1 "C causes an in- whereas the part composed of species growing at the northern limit of their natural geographical domain, are in re- gression. The ground coverage is dimin- ishing, e.g. for the genus Proustia for which very few or no young specimens are found. On the other hand, the dis- covery of very old Balsamocarpon bushes, in the quebrada west of La Silla, indicates that the local conditions have been quasi stable for centuries. This bush is characteristic of the illrd and lVth region, and able to survive during com- pletely dry years in dormant mode by loosing its leaves. The oldest stem shows about 700 growth rings and, de- Figure 12: The limits in latitude and altitude of the absolute desert and semi-arid area, at the pending on the fraction of years without present epoch (- - - -) and (- . - . -) respectively, and during the warm episode at the end of growth, its age possibly exceeds that the Peistocene. The arrows indicate the effect of a global climatic warming. Adapted from figure. Lauer (1986). crease of precipitation by a factor of four climate changes (warmer or colder). The Fuenzalida, H., 1983, Proceedings of the or more. occurrence of rainfall is barely related to ESO Workshop "Site Testing for Future Large Telescopes", La Silla, 4-6 October In northern Chile, between latitude the El NiRo phenomenon. All the climatic indicators considered 1983. 24'30 S and 25 "S, influences of polar Hoffmann, A. E., 1989, Cactaceas en la flora fronts and easterlies are at a minimum. here, biogeographic and meteorologi- silvestre de Chile. Ed. Fundacion Claudio Cloudiness and precipitation increase cal, lead to the conclusion that Paranal Gay, Santiago de Chile. from the west to the east; thus, coastal mountain is located in the best possible Huber, A,, 1979, "Estimacion empirica de las cordillera summits have to be preferred. area of South America for the settlement caracteristicas hidrologicas de Chile", On that mountain range, the azoic zone of a modern astronomical observatory. Agro Sur 7, 57-65. over 1500 m extends from 24'20 S to Lauer, W., 1986, Ber. Deutsch. Bot. Ges., 99, 26'10 S. Absolute desert is limited to a 21 1. Bibliography Perez, V.Q., 1983, Geographia de Chile 111, strip of 80-1 10 km wide, and possibly Arroyo, M.T.K., 1988, Ann. Missouri Bot. Biographia lnstituto Geographic0 Militar. due to a purely altitudinal effect, as Card, 75, 55-78. Rodriguez, C. R., 1988, "Plantas para lefia en narrow as 30 km at the latitude of Para- Caviedes, G. N., 1990, Climatic Change, 16, el Sur-occidente de Puno" proyecto ar- nal. The aridity of the western cordillera 99. bolandino, Punto, Peru. area, north of 265, appears to be Donoso-Barros, R., 1966, Reptiles in Chile, Weischet, W., 1966, Freiburger Universitats- stable, even in case of large amplitude Ed. Univ. de Chile, Santiago. blatter, 12, 53-68.

Progress on the VLT Mirror Cell Design

The NOTSA group at Risczr (Denmark) and time-effective and decided to build able, time consuming and . . . some- is performing, under contract of ESO, several models with copper wire which times may reach the manufacturing the engineering of the VLT primary can easily be soldered and rapidly mod- stage while still undetected. mirror cell. ified. This approach has effectively per- The two photographs show one of A preliminary design has now been mitted to discriminate rapidly between these "hardwire" models, once with a produced which however still needs to several designs, which would have had half mirror cardboard model, once with- be optimized through computer model- required much more effort through com- out. The actual VLT mirror cell will have ling and finite element analysis. The puter modelling. It also permitted to a diameter of about 9 metres and it will NOTSA group thought that a preliminary correct for a few errors which for such a be 3 metres high. "hardwire" modelling would be cost- complex structure are almost unavoid- D. ENARD, ESO

Halley Enters Hibernation

Famous Comet Halley, now receding CCD camera attached to the Danish Exposures totalling 980 min (16 hrs from the Sun after its perihelion passage 1.5-m telescope at La Silla. The seeing 20 min) were obtained and the "nega- in early 1986, has recently entered into a conditions were mediocre, - 1.3 arcsec. tive" picture shown here is a composite state of hibernation which will last until At this time Halley was 11.6 AU (1735 of 23 frames, each individually cleaned. shortly before the next passage in 2061. million km) and 12.5 AU (1870 million The image of Halley at the centre is This is the main result of a series of km) from the Earth and the Sun, respec- pointlike; the straight lines are trails of observations in late February 1990, dur- tively, that is well outside the orbit of the stars and galaxies in the field, because ing which the comet was imaged with a giant planet Saturn. the telescope was set to follow the com- et's motion. The mean, visual brightness of Halley during the observing period was V = 24.4 mag and the brightness varied between approx. 23.7 and 25.0 mag. The field covered is 39 x 39 arcsec (84 pixels square); North is up and East is to the left. The measured magnitude is about 0.35 mag brighter than what would be expected from Halley's nucleus alone, an avocado-shaped, 15 km long "dirty snowball", consisting of a variety of ices and dust. The brightness variations are caused by the tumbling motion of this nucleus, whereby the amount of re- flected sunlight depends on the chang- ing profile seen from the Earth. Of particular interest is the fact that the extended coma (i.e. the dust cloud around the nucleus), which was ob- served with the same telescope in 1989 at heliocentric distance 10.1 AU (see the Messenger 56, p. 45; June 1989), has now completely disappeared. In fact, no coma is visible at the 29 mag/sq.arcsec surface brightness level, corresponding to 1500 times less than the sky back- ground emission. It is therefore fairly certain that the release of dust from the nucleus must have ceased somewhere between 10.1 and 12.5 AU heliocentric distance. The former coma has now dispersed into the surrounding space and it is no longer being replenished by dust from the nu- cleus. In other words, Halley seems to picture indicates that it is somewhat This will most probably not be the last have entered a long period of hiberna- elongated in the direction opposite to image of Halley obtained during the tion which is likely to last until about the Sun. Together with the extra light present passage. Modern, large reflec- early 2061 when it again comes within observed, this could mean that a very tors are able to image objects of 27th about 5 AU from the Sun and will again low level of activity is still present and magnitude or even fainter, so it should be awakened by the sunlight. that there may still be some dust in the be possible to follow this famous comet Still, an accurate evaluation of the immediate neighbourhood of the nu- some years more. seemingly point-like image seen on this cleus. R. M. WEST, ESO

Minor Planet Named After Lo Woltjer

In the most recent issue of the Minor Planet Circulars, published by the Minor Planet Bureau of the IAU, the following naming of a minor planet is found on page 16591: "(3377) Lodewijk = 41 22 P-L Discovered 1960 Sept. 24 by C. J. van Houten and I. van Houten-Groeneveld on Palomar Schmidt plates taken by T. Gehrels. Named in honor of Lodewijk Woltjer, former editor of the Astronomical Jour- We congratulate Lo Woltjer to this tion, it is seen as a short trail on this blue nal and former director of the European extremely well-deserved honour and 60-min exposure. On this date, Southern Observatory, well known for show here a picture of his minor planet, "Lodewijk" was near opposition at a his studies on the Crab nebula. Name obtained on 17 April 1988 with the ESO geocentric distance of 308 million proposed by J. H. Oort." Schmidt telescope. Because of its mo- kilometres. The Editor PROFILE OF A KEY PROGRAMME: Investigation of the Galactic Distribution and Physical Properties of Carbon Stars T. LE BERTRE*, ESO N. EPCHTEIN and P. FOUQUE, Paris Observatory, France J. HRON and F. KERSCHBAUM, Vienna Observatory, Austria J, L EPINE, Sa"o Paulo University, Brazil

After leaving the main sequence, stars in carbon of the stellar surface. The car- mass loss during this phase. Although of intermediate mass (1 < M/Mo < 8) bon to oxygen (C/O) abundance ratio we understand in broad lines the evolu- evolve through various stagesu con- being normally inferior to 1, the surface tion of the stars through the AGB, our trolled by helium and hydrogen com- composition is in general oxygen-rich knowledge is often only qualitative and bustion. In one of these stages, called and the stars are said to be of M-type. many relevant points stay unclear. For the asymptotic giant branch (AGB), hy- However, at each thermal pulse, the sur- instance, the formation and evolution of drogen and helium burn alternately in face C/O ratio increases and, in some carbon stars are still the subject of dif- shells around an electron degenerate cases, can reach a value larger than 1, ferent interpretations. Also, the mass carbon-oxygen core [I]. This core re- meaning that the surface composition loss phenomenon is not well under- sults from the complete combustion of becomes carbon-rich (C-type). This stood quantitatively; numerical models helium during previous phases. Due to mechanism is thought to be responsible show that the stellar evolution through the high electronic thermal conductivity, for most of the carbon stars (at least the AGB and later is strongly dependent its temperature is insufficient for carbon those on the AGB) in our Galaxy. on the mass loss history. Parameters ignition. At the beginning of the evolu- The hydrogen envelope is unstable such as helium abundance and metal- tion through the AGB, helium burns and more or less regular pulsations de- licity (and in general individual element through triple-alpha reaction in a shell velop in it. Stars on the AGB are abundances) might have a strong influ- around the core which thus increases classified, sometimes arbitrarily , as irre- ence on stellar evolution and, in particu- its mass (early AGB). This shell dis- gular, semi-regular or mira variables. It lar, on carbon star formation; however, appears progressively leading to the ig- is thought that the regular pulsations of there is a lack of observational data in nition of hydrogen in the surrounding miras appear during the quiet phase of that field. shell. This second source of energy be- hydrogen burning; in general, their Finally, these objects during their comes progressively dominant. periods range from 100 to 500 days, but phases of mass loss appear to be major As a consequence, the mass of the in some extreme cases may be larger. contributors to the replenishment of helium shell increases until helium is Following a thermal pulse, the star is the interstellar medium. The knowledge reignited violently in it (thermal pulse), thought to become an irregular pulsator of the composition and of the total re- then burns quietly while hydrogen in the of lower luminosity. turn rate of the matter that they are upper shell stops burning. The star may Also, through a mechanism which is injecting into the interstellar medium at experience 10 to 20 such cycles of still not well understood but which different galacto-centric distances is of - lo5 years duration. During 10% of appears related to the pulsations, the basic importance for describing the each cycle, the dominant source of stellar atmosphere is extended well chemical evolution of the Galaxy. This energy is helium combustion, and, dur- above the photospheric radius (Rphot- requires an accurate census of the AGB ing the remaining 90%, hydrogen com- 1 A.U.). In some cases, it can reach stars as a function of their location, type bustion. When helium is burning, the such a large dimension (- 10 Rphot)that, and mass loss rate. output luminosity of the star should be in its upper layers, refractory elements In our approach of these problems, lower by 0.5-1 magnitude than when condense into dust. Dust formation has we concentrate on galactic carbon stars hydrogen is burning. This phase of the drastic consequences. Radiation which are presently undergoing mass AGB - when helium and hydrogen are pressure on grains accelerate them loss. Optical surveys are known to be burning alternately - is referred to as the away from the central star and, in their biased against mass losing carbon thermally pulsing AGB (TP-AGB) and of- motion, they drag the gas outwards. In stars; also, due to the interstellar ab- ten, by ellipsis, the AGB. After the AGB, these conditions, the star becomes sorption, they are limited to the solar the star evolves quickly (in -lO3- surrounded by an expanding envelope neighbourhood. However, we have de- lo4 years) toward the planetary nebula of gas and dust. This mass loss veloped a selection method of such ob- stage at approximately constant lumi- phenomenon occurs preferentially dur- jects which is based on near-infrared nosity and then dies out as a white ing the Mira phases; however, some ir- (1 to 5 pm) and IRAS (12 and 25 pm) dwarf whose temperature and luminosi- regular and semi-regular pulsators are photometric data and which has been ty steadily decrease. known to be also losing mass, whereas shown to be efficient and safe [2]. Start- The shells in which nuclear combus- some miras, especially among those of ing from the IRAS LRS data base, we tion occurs are surrounded by a large short period (<350 days), do not appear have then studied the carbon stars in convective hydrogen envelope. Follow- to be undergoing significant mass loss. the solar neighbourhood [3]. We now ing a thermal pulse, material processed The TP-AGB corresponds to a rela- want to extend our study to several lo- by the triple-alpha reaction can be con- tively short stage of the stellar evolution cations in the Galaxy, namely the disk at vected upward leading to an enrichment (lo6-1 O7 years). However, its study is different galacto-centric distances and very important, because stars are height above the galactic plane, by sur-

* Present address: DEMIRM, Observatoire de Paris, reaching their maximum luminosity veying, in an unbiased way, the mass 92195 Meudon Principal Cedex, France. (- 1O4 Lg) and experience most of their losing AGB population in the galactic centre and anti-centre directions, and at metallicity depends on the galacto-cen- References different galactic latitudes. tric distance, its effect on the formation [l] Iben, 1.: 1981, in Physical Processes in For every sub-sample, the distribu- and evolution of carbon stars will be Red Giants, ed. by I. lben and A. Renzini, tions of objects in function of their sorted out. Also, the mass-return rate p. 3. bolometric luminosities and mass loss from carbon stars will be determined as [2] Epchtein, N., Le Bertre, T., Lepine, rates will be evaluated. As the samples a function of the distance to the galactic J. R. D., Marques dos Santos, P., Matsuu- contain stars of different pulsational be- centre. ra, O.T., Picazzio, E.: 1987, Astron. Astro- haviours, the relationships between type This investigation will thus cast new phys. Suppl. Ser. 71, 39. [3] Epchtein, N., Le Bertre, T., Lepine, of variability, luminosity and mass loss light on the physical properties of car- J. R. D.: 1990, Astron. Astrophys. 227, 82. rate will be investigated. Initial masses bon stars in different physical and of carbon star progenitors will be de- chemical environments, and on the rived through their distribution perpen- chemical evolution of the interstellar dicularly to the galactic plane. Because medium throughout the Galaxy.

PROFILE OF A KEY PROGRAMME: High Precision Radial Velocity Determinations for the Study of the Internal Kinematical and Dynamical Structure and Evolution of Young Stellar Groups H. HENSBERGE, E. L. VAN DESSEL, M. BURGER, Royal Observatoryof Belgium P. T. DEZEEUW, J. LUB, R. S. LEPOOLE, University of Leiden, the Netherlands W. VERSCHUEREN, M. DAVID, T. THEUNS, C. DE LOORE, University ofAntwerp, Belgium E. J. DE GEUS, University of Maryland, USA R. D. MATHIEU, University of Wisconsin, USA A. BLAAUW, Universities of Leiden and Groningen, the Netherlands

Purpose is at the point that makes such observa- mation on the dynamical state of young Presently observable sites of star for- tional efforts feasible. CCD echelle stellar systems is essential as input in mation corroborate the viewpoint that spectroscopy on ground-based tele- such numerical experiments and in the birth of stars occurs in groups. Such scopes offers the opportunity to record theoretical models. groups remain gravitationally bound for good quality (SIN >50) spectra over the a shorter or a longer time interval and extended wavelength range required in Interpretation of the Data are catalogued as open star clusters or order to acquire sufficient spectral infor- associations depending on their com- mation in early-type stars. CASPEC at The determination of RVs in early- pactness. As far as the dynamical state the 3.6-m ESO telescope provides the type stars with the required precision is, of these groups is governed by the con- stability and efficiency to obtain a for several reasons, a challenge. The ditions in the initial phases of cloud frag- reasonably large set of radial velocities application of CORAVEL in RV work has mentation, star formation and nebular (RVs) with an accuracy that is limited by opened new frontiers in the study of gas expulsion, they contain valuable in- stellar atmosphere physics or standard late-type stars, based on a high quality formation about the star birth processes system calibration rather than by the RV standard system. The use of the and the early dynamical evolution of a instrument. We concentrate on the 3 CORAVEL technique is unfortunately star forming region (1). Evidently, the subgroups in the Sco-Cen 06associa- not extendable to earlier types. The es- younger the groups, the more the pres- tion and on the more distant young clus- tablishment of a better standard system ent state reflects the initial characteris- ter NGC 2244 in the Rosette nebula, at early spectral types is still essential tics. aiming at a detailed survey of about and our observations are expected to An important key to the progress in 500 0-F type respectively 50 0-A0 type contribute to this task (9). RVs will be such studies is the availability of infor- stars. The radial velocity study is part of measured by the cross-correlation tech- mation on the internal kinematics in stel- a continuing observing programme on nique (1 O), although attention will have lar groups: the internal velocity disper- nearby clusters and associations, in- to be paid to discern systematic effects sion, and its spatial and stellar mass cluding Walraven photometry (4, 5, 6), possibly originating from subsystems of dependence (2). That purpose imposes astrometry from HIPPARCOS, mapping spectral lines; systematic atmospheric an accuracy of the order of a few kmls of molecular gas (7), and spectroscopy motions in OB stars might bias the ap- on empirically derived kinematical quan- for classification (6). The theoretical side parent RVs and could be detectable tities for a considerable number of stars of our study consists of N-body hydro- from lines formed over different atmo- covering a large range in stellar mass dynamical simulations of stars embed- spherical depths. As a by-product, this (3). Nowadays, instrumental technology ded in gas (8). Reliable empirical infor- should almost certainly lead to addition- al insights into the atmospheric struc- ture of hot stars. It is essential, although time consum- ing, to disentangle effects due to binari- ty from effects reflecting the kinematics of the stellar group (11). Especially the lack of recognition of wider binaries with an RV amplitude of the order of 10 kmls might significantly influence the conclu- sions. Hence, repetition of RV observa- tions is necessary and will in turn in- crease our knowledge on binarity in the selected young stellar groups. The spectra will in addition allow a study of stellar rotation in these star groups (12). In many respects, this project forms an extension towards the earliest spec- tral types of the key programmes of Mayor et al. and Gerbaldi et al. (de- scribed in the Messenger 56), even when the primary scientific motivation is somewhat different. In addition to the common interest in radial velocities, the stars in Sco-Cen are also observed by the Hipparcos satellite, providing space motions when combined with the RVs. Using these, we hope to reconstruct the initial minimal volumes in which the star formation occurred which gave rise to the presently expanding Sco-Cen sub- 4180 4200 4220 4240 4260 4280 groups, and to discuss the possibility of wavelength (angstrom) sequential star formation (13). Part of the CASPEC spectrum of NGC 2244-201, a 10th magnitude B 1 V star. The strongest lines are 011 4185, 011 4 190, NII 4242, 011 4254, CII 4267, a complex of 011 lines around First Results 4277A, 011 4283, Slll4285 and 011 4286. Strictly within the frame of the key programme, the first spectra have been obtained on 3 nights in May 1990. How- References 8. Theuns, T.: 1990, in Proc. Xlth ERAM ever, a limited amount of data has been (Tenerife, July 1989), in press. obtained during the last three years 1. Lada, C. J.: 1987, IAU Symp. 115, 1. 9. Fekel, F. C.: 1985, IAU Coll. 88, 335. with CASPEC and has resulted in the 2. Duerr, R., Imhoff, C.L., Lada, C.J.: 1982, 10. Wyatt, W. F.: 1985, IAU Coll. 88, 123. establishment of a stable, accurate Astrophys. J. 261, 135. 11. Mathieu, R. D.: 1985, IAU Coll. 88, 249. wavelength calibration procedure (14) 3. Mathieu, R. D.: 1986, Highlights of As- 12. Hartmann, L., Hewett, R., Stahler, S., and an optimized echelle reduction tronomy, 7, 481. Mathieu, R. D.: 1986, Astrophys. J. 309, method (15). Presently, we can concen- 4. De Geus, E. J., Lub, J., van de Grift: 1990, 275. trate on the proper radial velocity work. Astron. Astrophys. Suppl. (in press). 13. Sargent, A. I.: 1985, in: Birth and Evolu- In NGC 2244 we detected a number of 5. De Geus, E.J., De Zeeuw, P.T., Lub, J.: tion of Massive Stars and Stellar Groups, 1989, Astron. Astrophys. 216, 44. eds. W. Boland and H. Van Woerden (Dor- slowly rotating 0 and B stars (out of our 6. Verschueren, W., Hensberge, H., de drecht, Reidel), p. 5. current sample of 17, 5 had v.sin i Loore, C.: 1990, in Proc. Xlth ERAM 14. Hensberge, H., Verschueren, W.: 1989, <30 kmls), whose narrow lines are (Tenerife, July 1989), in press. The Messenger 58, 51. favourable to a very accurate determi- 7. De Geus, E.J., Bronfman, L., Thaddeus, 15. Verschueren, W., Hensberge, H.: 1990, nation of the RV (Fig. 1). P.: 1990, Astron. Astrophys. 231, 137. Astron. Astrophys., in press.

The Status of the Hubble Space Telescope

As you have certainly learnt from the resulting Point Spread Function is vents HST to reach its "level 1" specifi- news media, the focussing tests carried characterized by a sharp core of about cations (about 70% encircled energy out during last June revealed that the 0.1 arcsec surrounded by an extended within 0.1 arcsec) and has serious con- Hubble Space Telescope suffers from "halo": unfortunately the core encircles sequences on its imaging capabilities, spherical aberration. The amplitude of only about 10-20 % of the energy. The the actual impact on the scientific output the aberration is about half a wavelength forthcoming issues of the ST Scl and ST- has to be evaluated a bit more carefully rms and it has a negative sign, i.e. the ECF Newsletters will contain more quan- than what has been unfortunately done marginal focus lays further away from the titative details on the problem. by the generic press. In particular, any secondary than the paraxial one. The Although the spherical aberration pre- comparison with the capabilities of ground-based telescopes has to consid- relevant data will be made available to performance will be reviewed in the com- er the uniqueness of the UV imag- interested scientists shortly after the ob- ing weeks. ing from space and the fact that, since servation. Concurrently the Guarantied Considerable effort is also being in- the HST Point Spread Function de- Time Observers and General Observers' vested in evaluating the applicability of parts considerably from a gaussian-like proposals are being reviewed for feasi- different image restoration methods. profile, spatial resolutions cannot be bility and modification. More about this ECF staff, in collaboration with ESO col- compared just by using the FWHM as a exercise will be published in the ST leagues, is experimenting with different parameter. Moreover, the two HST spec- Newsletters, in the electronic Bulletin algorithms on simulated images which trographs are less affected than the Board and communicated directly to the make use of the actual, aberrated, HST cameras and most of the scientific pro- HST Principal Investigators. psf. The results will be presented to a grams should still be feasible, albeit with On the front of correcting the problem, specific workshop on the subject which an increase in the exposure times. NASA intends to speed up the construc- has been organized by the ST Science Currently, a Scientific Assessment tion of the second generation instru- Institute on August 21 -22. Meanwhile Team has been formed at the ST Science ments, in particular of the WF/PC II, the ECF continues to maintain contact Institute with the task of preparing an which will include appropriate modifica- with the European PIS who are involved observing programme (to be carried out tions in the optical design to compensate in Cycle 1 observations offering assist- in August-September) which will allow a for the spherical aberration of the tele- ance in the review and possible modifi- better evaluation of the actual perfor- scope. The situation of the ESA Faint cation of their programmes. mance of the scientific instruments. The Object Camera in the light of the HST P. BENVENUTI, ST-ECF

"Matching Error" (Spherical Aberration) in the Hubble Space Telescope (HST): Some Technical Comments R. N. WILSON, ESO

Much consternation has been caused probably the opposite. The distance A0 aberration" which gives the maximum in the astronomical community because is called the longitudinal spherical aber- phase error of the image forming light. of the revelations since the last week of ration and is about 40 mm in the HST. If This is 4.34 ym for the above figures and June that the Hubble Space Telescope the focus for the detector is chosen to an aperture of 2.4 m for the HST. This (HST) has a systematic error giving an be at 0 (the so-called paraxial or Gauss- wavefront aberration is the best physical image with about 70 % of the geometri- ian focus), then the total transverse measure of the error and is, in fact, cal light energy within about 1.5 arcsec spread of the light has the diameter BC. exactly twice the maximum error on the diameter instead of less than the 0.1 It can be shown that, for the basic (so- mirror surface involved, referred to the arcsec predicted from its specification called "third order") spherical aberra- Gaussian focus, which is therefore of "diffraction limited performance" for tion, the optimum focus reducing the 2.17 km. Frequently, the rms (root mean visible light (wavelength 500 nm). The diameter of the light patch to a minimum square) error on the surface has been error has been identified as mainly is at D, one quarter of the distance from quoted which is about one sixth of the spherical aberration due to "matching A to 0. This minimum diameter is called above, or 0.36 km, or somewhat more error". The above quality figure has the "disk of least confusion" EF which is than half a wavelength of laser light of been quoted in a number of reports, but obviously one quarter of BC. Taking A0 0.632 km. The above figures reveal how may include other errors (including re- as about 40 mm in the HST, an exit essential it is to define exactly what de- sidual focus error) of unknown amount. beam of f/24, the diameter BC contain- finition is being used, otherwise serious From more specific information on the ing I00 % of the energy at the Gaussian confusion results. amount of spherical aberration, I have focus is 6.0 arcsec; at the best focus it is Let us now return to the probable calculated below that the spherical 1.5 arcsec. These figures, expressing origin of this spherical aberration error in aberration error alone would give an im- angular aberration, can easily be con- the HST. age at best focus with 100% of the verted into the so-called "wavefront In the technical domain of the produc- geometrical light energy within about 1.5 arcsec diameter. Before considering further the origins of this error, let us look at the meaning of the term "spherical aberration". Elementary text books on optics usually explain it as a "longitudinal aberration" as shown in Figure 1. Rays coming from the central part of the optical system (near its axis) focus at the point 0 on the axis, whereas those from the outer cir- cumference focus at A. The sign of the aberration as shown above with A to the left of 0 is what a simple convex lens would generate, whereas in the HST it is Figure 1 : Path of rays forming an image afflicted with spherical aberration. that the bas~cform of the two mlrrors w~ll,In comb~nat~on,give an Image free from spher~calaberratlon at the nom~nal Cassegra~nfocus. For other errors over point source the surface such as astlgmatlsm or h~gh &g!? spatlal frequency errors, some other test --- of the whole surface IS required and F various posslb~l~t~esexlst [2]. The Pentaprlsm Test (see Fig. 3) was probably f~rst Invented by Wetthauer and Brodhun In 1920 [3] and has been systemat~cally used by a number of manufacturers, for example REOSC In F~gure2. Autocoll~mat~ontest of a Cassegraln telescope ~nfunctional geometry agalnst a plane [4]1 have a~~lledIt rOutlnel~ mlrror A polnt source at the nomlnal focus F sends a Ilght beam backwards through the ~11thgreat Success for 25 Years or more, telescope whlch IS reflected back ln the same path by the plane m~rrorM3 The lmage formed or Korhonen In the SUCC~SS~U~manufac- at F contalns the errors of M 1 and M2 doubled by the double pass Any errors of M3 are also ture of the opt~csof the recently com- lmprlnted on the lmage In practlce, a plane mlrror M3 of adequate quallty IS proh~blt~vely pleted 2,5-m Nordic Optical Telescope. expensive and d~fficultto produce for diameters above 1 m The errors ln the lmage at Fare was also used already In 1939 In the measured by an lmage analyser, usually an Interferometer or a Shack-Hartmann devlce Un~tedStates by Hendr~xand Chrlstle [5] In connect~onw~th Schm~dt systems, and descr~bedby Hochgraf [6] In 1969. It seems surprlslng that thls test, whlch t~onof large preclslon opt~cs,the danger are not rigorously respected. But there IS s~mpleand cheap to set up (w~ththe of such "matchlng error" IS well known. IS one test of secondar~eswhlch effec- system axis e~therhor~zontal or vert~cal), A complete funct~onaltest of a com- tlvely ensures that such "matchlng was not appl~edto the HST, slnce ~t b~nedCassegraln system (see Flg. 2) error" cannot occur. Thls IS the so- would certa~nlyhave revealed the error. cannot be performed for apertures called "Pentaprlsm Test". In fact, the However, ~tsuse IS by no means general above about 1 m since a plane mlrror of Pentaprlsm Test IS only a test of the in the manufacture of ground-based te- the excellent qual~tyrequ~red does not spher~calaberrat~on, 1.e. a test to ensure lescopes wh~chexplains why "match~ng ex~stfor larger apertures - even a I-m d~ameterflat IS a rare and very expen- sive element. However, there are other rail poss~bll~t~esfor testing for "matchrng t error" In a funct~onal way, as shown I below. I In practlce, the primary mlrrors of I modern large telescopes are tested In I autocoll~mat~onat their centres of curva- I I ture, the errors be~ngdeterm~ned by In- I terferometr~cor Hartmann type analys~s I of the Image. Since modern, short prlmarles are strongly aspher~c(sl~ghtly hyperbol~cfor R~tchey-Chret~entype te- lescopes) the autocoll~mat~onImage IS strongly aberrated. Thls aberrat~on IS normally compensated by a so-called "compensat~on" or "null" system, so that the errors can be referred to a corrected Image. Th~skey technology was flrst proposed by the Engl~sh amateur Horace Dall In 1947 [I] and IS the basis of most modern mirror testing. sighting telescope The "null system" must be correct to very high precision, in its design, graticule manufacture and in its positioning in the test set-up - otherwise a systematic Figure 3: The Pentaprism Test: As in Figure 2, a pinhole source at the nominal focus sends a error arises which is spherical aberration beam of light backwards through the telescope. Instead of being reflected back by a large in its classic form. plane mirror, a small part of the parallel beam enters the face ab of a pentaprism which can be Cassegrain secondaries are more moved along a rail across the diameter of the telescope. After reflections at faces cd and ea of difficult to test because they are convex the pentaprism, the selected beam emerges via face cd deflected about 90 9 A fixed sighting and cannot deliver a real image without telescope ST, firmly mounted, measures the direction of the beam by observing the image F' of an ancillary system. Testing of convex F on a graticule. The basis of the test is that, in the section shown in the diagram, the deflection secondaries is a whole technological of a pentaprism is unaltered by small rotations of the pentaprism about an axis perpendicular to the plane of the paper. Such small rotations of the pentaprism are unavoidable in moving it area in its own right [2]. However, the across the diameter, but have no effect on the angles measured in the plane of measurement. test methods will all have tolerances Thus one can measure directly the differences of angle of the small beams as the pentaprism is (more or less severe, depending on the moved over the telescope diameter. This measures directly the angular spherical aberration, method) which will lead to a similar sys- from which integration gives the wavefront aberration. Other errors, such as defocus and tematic spherical aberration error if they coma, can be eliminated as they have a different dependence on distance from the axis. error", often very large, has been a com- also a test with an independent IR sys- ably only a retouch of astigmatism mon technical error. One telescope tem working at a wavelength of 10 pm. would be possible with them. So the where this happened was the Canada- Although the resolution of the IR system HST is effectively a passive telescope France-Hawaii-Telescope (CFHT), for was about 16 times lower than that of so far as bending (correcting) the prima- which the spherical aberration was af- the visible one, it was considered by ry is concerned. For this situation, the terwards successfully corrected by Carl Zeiss that an error exceeding the pentaprism test would have been the bending the secondary (a case of dc- tolerance would be detected by the best guarantee against matching error. fixed-active correction at the secon- comparison between the two systems. It is reliable, simple and cheap. dary). (In fact, the matching error made was Statements have been made that the The Nl7 also had a matching error, detected in this way, but was believed current performance of the HST is as provoked by a systematic error in posi- to be still just within the measuring noise good as the best ground-based tele- tioning of the compensation systems - all other errors showed excellent scopes. This is certainly not true. Apart used in testing the primary. Although agreement between the two test sys- from the Nl7 which - because of its this error was small (1.8 mm in a test tems). Because of the tight time active optics, very "smooth" mirrors and distance of about 15.4 m) the spherical schedule, ESO and Carl Zeiss agreed to building concept - routinely produces aberration error introduced had a coef- drop the pentaprism test in view of the total images at the excellent La Silla site ficient (i.e. peak-to-valley wavefront above cross-check security of the tests with a d,, (i. e. diameter containing 70 % aberration) of about 3000 nm. This cor- and the considerable dynamic range of of the geometrical light energy) of less responds to an image diameter, for this correction of the active optics system. than 0.5 arcsec, there are a number of effect alone, containing 100% of the This decision was subsequently val- excellent "passive" telescopes in opera- geometrical light energy, of 0.71 arcsec idated by our ability to achieve complete tion (including the William Herschel Te- at optimum focus. Although this was correction actively of the matching error lescope) capable under favourable see- outside the so-called "passive" specifi- as well as all other actively controllable ing conditions of producing total images cation, we were able to correct it com- errors in the system, giving the spec- with a d70 well under 1 arcsec. In con- pletely by the first (fixed) level of the tacular image quality results of the Nl7 trast, the HST has a d,, from given data active optics system of the Nn,as has [7]. The essential feature of the figuring of about 1 arcsec from the spherical been reported in our recent paper "Ac- work by Carl Zeiss was the excellent aberration alone. tive optics IV" [7]. quality regarding the more rapidly vary- It is interesting to consider the deci- ing (higher frequency) defects on the sions taken with respect to a possible surfaces such as zones or local hills and Literature matching error at the time of the con- hollows, for which they were well inside 1. H. E. Dall, 1947, J. Brit. Astron. Ass., 57 (5) tractual discussions for the optics of the the very hard specification. Thus the also 1953, Amateur Telescope Making, Nl7. At that time, the author proposed excellent work of Carl Zeiss and the NTT Book 3, Scientific American Inc., 149. to the manufacturer, Carl Zeiss, that a active optics system were both essen- 2. R. N. Wilson, 1974, ESO Technical Report pentaprism test be done to ensure that tial and complementary to each other No. 3, July 1974. matching error would be negligible. for the success of the final optical 3. Wetthauer and Brodhun, 1920, Zeitschrift However, the active optics concept system. f. lnstrumentenkunde 40, 96. allows relaxed tolerances precisely for The HST, by contrast, has a very stiff, 4. J. Espiard and B. Favre, 1970, Nouvelle such errors as spherical aberration (this lightweighted, egg-crate type of prima- Rev. d'optique appliquee, 1 (6), 395. 5. D.O. Hendrix and W.H. Christie, 1939, is one of its two principal aims) and a ry. From its nature, the dynamic range Scientific American, August 1939. relaxation up to a coefficient of the order available with the 24 actuators operat- 6. Hochgraf, 1969, Opt. Sci. Center Newslet- of 2000 nm was proposed. Furthermore, ing on the primary must be far too small ter, Jan.-March 1969, 41. the test procedures for primary and sec- to permit correction of a matching error 7. R.N. Wilson, F. Franza, L. Noethe and G. ondary comprised not only tests at the significantly larger than that of the NTT Andreoni, 1990, ESO Technical Preprint normal visible wavelength (632 nm) but in terms of wavefront aberration. Prob- No. 24, May 1990.

HST Images: What Can Image Processing Do? D. BAADE and L. B. LUCY, ESO

In these first days after the actual data achievable with the present instru- 1989), which combines deconvolution image quality of the Hubble Space Tele- mental configuration. with a simultaneous resampling to a scope has become known, two lines of smaller pixel size. In that particular im- effort to achieve improvements are be- Previous Work plementation, an iterative deconvolution ing mentioned most often: optical method (Lucy, 1974) was used, but our correctors in the second generation Originally, image restoration algo- technique of simultaneous resampling instruments and numerical image pro- rithms were thought to be desirable can in principle be mated with other cessing - i.e., deconvolution. The first for HST data because most of the imag- image restoration algorithms, e.g., the measure will undoubtedly be more ing modes would undersample the anti- maximum entropy method. Indeed, effective but its realization will take at cipated point spread function (PSF). We such tests as have been carried out least 2% years. Deconvolution, on the therefore developed and implemented (Heasley, 1984) indicate that the max- other hand, can be applied already to one such technique (Lucy and Baade, imum entropy method will yield results As can partly be seen in Figure 1, the PSF has a very narrow core which, in some observations, has been found to be as narrow as 0.07 arcsec FWHM but to contain only about 15% of the total flux. This shows that, in spite of the broad wings, there is still genuine high- frequency information in HST images and that this is only sparsely sampled. In order, therefore, to test the ability of our technique to recover some of this high- frequency information, we have simu- lated observations of a double-star in the following way: Star A, of total flux 3000 units, is located at fractional coor- dinates (0.7, 0.4) pixels. Star B is 2.5 times (i.e., 1 mag) brighter and is shifted with respect to Star A by (-4.1, -1.3) pixels, which corresponds to a separa- tion of 0.43 arcsec or just over 2 times the FWHM of the PSF. Neither stellar profile includes noise, but a background with an average flux of 50 units per pixel and Poissonian noise has been added. The raw image as well as the results of 10 and 20 iterations of the deconvolu- tion algorithm with simultaneous re- sampling by a factor of 3 in both dimen- sions are shown in Figure 3. From other experiments with our Arcsec method, we have found that, with a Figure 1 : Central cuts through the adopted and the originally specified (shaded) point spread Gaussian PSF, a necessary condition functions of HST sampled with 0.1 arcsec pixels. Both PSF's are normalized to the same total for it to be able to separate two point flux but the adopted PSF is plotted on a 10 times expanded flux scale. sources is that along the line connect- ing the centres of the two sources a local minimum occurs. (For example, two stars of equal brightness usually need to be separated by more than one closely comparable to those presented (or, conversely, how big the gain over FWHM.) This makes sense because herein. conventional ground-based observa- without further information it is other- Readers of the Messenger have al- tions could have been). Note that the wise impossible to distinguish between ready seen examples of the perfor- non-monotonic decline of the adopted, two point sources and a truly elon- mance of the deconvolution method in schematic PSF is in agreement with ac- gated, single object. Our double star No. 56, p. 3 and p. 35, where it was tual HST stellar images, which consist of just satisfies this condition. Generally, applied to the first NTT images and to a core and a ring-like outer halo. Since, in the ability to separate two closely 3.6-m telescope observations of the the absence of a real focus position, the spaced point sources depends on their nebulosities around SN 1987A, respec- definition of "the" PSF is in fact some- relative distance and their brightness tively. what blurred, our approximation should ratio. Because of the narrow core of the be good enough to test the viability of adopted PSF, the corresponding two- parameter space for the nominal per- Numerical Experiments deconvolution techniques for HST im- ages. This is the purpose of our present formance of HST appears relatively little In a note dated June 29 and posted on exercise. affected with respect to separation, the electronic bulletin board of the Space Our simulations assume a pixel size of whereas the constraint on the max- Telescope-European Coordination 0.1 arcsec and therefore correspond to imum allowable brightness ratio at a Facility, H.E. Bond and H.S. Stockman the case of the Wide Field Camera. Fig- given scale is strongly compromised. In (Space Telescope Science Institute, Bal- ure 2 illustrates the effects of decon- other words, the ability of HST to re- timore) provided the fractional encircled volution on a single noise-free point solve fine structures is not too severely energy at radii 0.1, 0.2, 0.3, 0.4, 0.5, 0.7, source with perfectly compensated (i. e., affected so long as their contrast differ- 1 .O, and 1.5 arcsec as measured with the black) background. As can be seen, by ence is small. Planetary Camera on board HST during going from 10 to 20 iterations - as In some sense, our input assumptions June 10-24. Under the assumption of would be appropriate for very high SIN represent a worst-case situation: The circular symmetry, we have used this data - the gain achieved is still worth the relative noise in the background is high, information to construct the PSF plotted effort. The comparison with the two the separation is small, and the sam- in Figure 1. This adopted PSF has a full PSF's of Figure 1 shows that although pling is the coarsest of all HST imaging width at half maximum (FWHM) of 0.2 the shortfall with respect to the original modes. We therefore infer that cameras arcsec (or two pixels). However, the specifications is still large, the improve- on board HST with imaging modes that comparison (Fig. 1) with the original ment over the raw data is even larger. In sample the reported 0.07 arcsec core of specifications for the PSF shows how these deconvolutions, the resampling the telescope's PSF better than in our dramatic the loss in contrast actually is option was turned off. crude simulation of the Wide Field Cam- model techniques are much more effec- tive than an assumption-free decon- volution. However, even then, a previ- ously applied, mild deconvolution could Deconvolved point source still be advantageous, as it provides a PSF-neutral smoothing, especially if the simultaneous resampling option is cho- sen. It may also help to recover part of the loss in limiting magnitude incurred because of the image spread.

Existing Options We conclude this brief report by pointing out that the tools we have been using here have, since the 1989 November release of ESO's MlDAS im- age processing system, been made generally available (command REBIN/ DECONVOLVE, context PHOTOM) so that anyone interested can repeat our experiments but tailor them more speci- fically for the needs of a particular ob- serving programme. Indeed, such ex- periments could determine whether the scientific goals of an approved imaging proposal can still be at least partly achieved. Note that the MlDAS im- plementation can accept any numerical representation of the PSF and does not Arcsec require axial symmetry. Thus, already Figure 2: The adopted PSF after 10 (shaded) and 20 deconvolution iterations, respectively. available is the option of carrying out Flux scales and total fluxes are the same as in Figure 1 for the specified PSF. deconvolutions using the highly struc- tured, two-dimensional observed PSF, which shows numerous spikes and rings. era will yield data from which image erable, especially with the resampling With respect to the resampling option, structure can be restored at spatial fre- option. However, given the other expen- it should perhaps be stressed that this is quencies that are presently still inac- ses of the HST project - or even only the implemented (Lucy and Baade, 1989) cessible to routine direct imaging from costs of replacing some of HST's instru- without any degradation of the observa- ground-based observatories. ments - this point is of relatively minor tional data. In contrast, this is not true Even on an array processor and after importance. Nevertheless, if the for the experiments reported by Evans vectorization of the code, the amount of assumption of point sources is justified et al. (1989) since their shifting and ad- computer time required for the decon- or other additional information is avail- ding procedure for introducing sub-pix- volution of a full 1600 x 1600 pixel able about the nature of a given struc- els represents a convolution applied to WFPC image will still be very consid- ture, PSF fitting and similar, source- the observed data.

I I Figure 3: The simulated binary star image described in the text. From left to right are shown the raw data (the false colour scale ranges from 30 to 220 flux units), and the results of 10 (high cut set to 530 units) and 20 (high cut 760 units) iterations of the deconvolution algorithm. In the raw data, the coarse 0.1 x 0.1 arcsec pixels are clearly seen. The deconvolved images are smoother partly because of the simultaneous resampling to a pixel size of 1/30 arcsec and partly because of the deconvolution algorithm's reluctance to introduce structure on a finer scale than the PSF allows. Potential Options A further possibility is to develop a References code that simultaneously deconvolves If required, the programme could be several images of the same field, each Adorf, H.-M.: 1989, in Proc. 1st ESO/ST-ECF extended to take account of the varia- of which is displaced by a fraction of a Data Analysis Workshop, eds. P.J. Gros- tion of the PSF with position in the focal pixel. b01, F. Murtagh, R.H. Warmels, p. 215. Evans, I.N., Ford, H.C., and Hui, X.: 1989, plane. This possibility, which has been in- Astrophys. J. 347, 68. vestigated theoretically by Adorf (1989), At present, the code assumes a spa- Heasley, J. N.: 1984, P.A.S.P. 96, 767. tially invariant PSF but, in contrast to, introduces an element of image recon- Lucy, L. B.: 1974, Astron. J., 79, 745. e.g., Fourier transform techniques, this struction by tomography and might well Lucy, L.B. and Baade, D.: 1989, in Proc. 1st assumption is not fundamentally de- be useful for certain objects with struc- ESO/ST-ECF Data Analysis Workshop, manded by the iterative deconvolution ture on the scale of the narrow core of eds. P. J. Grosberl, F. Murtagh, R.H. War- algorithm. the observed PSF. mels, p. 21 9.

ESO'S EARLY HISTORY, 1953- 1975 VIII. The 3.6-m Telescope Project; From Concept to the Late 1960's* A. BLAAUW, Kapteyn Laboratory, Groningen, the Netherlands "Le programme initial de I'Organisation compotfe la construction, I'installation et le fonctionnement d'un observatoire dans /'hemisphere austral, comprenant: a) un telescope d'environ 3 metres d'ouvetfure; - - -" From the ESO Convention, Art. 11.2.

Introduction servatory, however the ESO design among which descriptions of the two This article reviews work towards the soon deviated from this. recently completed largest instruments: realization of the 3.6-m telescope from Naturally, the designs of the various of the 200-inch Hale Telescope by Ira S. the early beginnings of ESO up to the components of the project are interre- Bowen, and of the Lick 120-inch by moment, at the end of 1969, when lated, but once a certain stage has been W. W. Baustian; and furthermore chap- Council drastically changed course. reached, the further development and ters on Design of Reflecting Telescopes These early years saw an Instrumenta- construction of the various parts tends by Aden B. Meinel; and on Schmidt tion Committee, a Directorate and an to proceed largely independently. For Camera's, again by Bowen. This Volume engineering bureau devoted to the crea- our project this was particularly so for, became a basic reference text for the tion of an instrument of dimensions and on the one hand, the housing of the next decades. costs, an order of magnitude larger than telescope, i.e. building and dome, and Another important event was IAU anything achieved so far in optical as- on the other hand the ensemble of tube, Symposium No. 27, "The Construction tronomy in Europe. Unfortunately, lack optics and mounting. Within the latter of Large Telescopes" held from 5 to 12 of experience proved to be a serious again a subdivision can be made: the April 1965 at Tucson, Arizona, and at drawback, and this unavoidably puts its combination tubeloptics, and the Pasadena and Mt. Hamilton (Lick Ob- stamp on the present, somewhat cheer- mounting plus drive. The account on the servatory) in California. The proceed- less, account. The new approach progress in the project can be sub- ings, edited by David L. Crawford and adopted by Council late 1969, will be divided accordingly. Up to the early published in 1966, contained much described in the next article. 1970's, the progress of the project as a basic information and instructive dis- whole was determined almost entirely cussion reports. Among the participants by the (lack of progress in the) design of from ESO countries were Baranne, Basic Concepts the mechanical parts of telescope tube Bahner, Courtes, Elsasser, Fehrenbach, A telescope project like the one for and mounting. Contrary to what seemed Heckmann, Ramberg and the engineer the ESO 3.6-m telescope, starts by to have been a tradition in earlier gener- who worked for ESO, W. Strewinski. In specifying the dimension of the main ations of large-telescope building, pro- the present context mentioning should mirror as this determines the light gress for the ESO 3.6-m telescope was be made also of K. Bahner's Chapter gathering power of the instrument, and not determined by the completion of the "Teleskope" in Handbuch der Physik, by choosing the desired focal ratios for optics. Vol. 29, 1967, and Bahner's article the different modes in which the instru- "Large and Very Large Telescopes; Pro- jects and Considerations" in ESO Bulle- ment is to be used; the Prime focus, the Early Conferences and Texts Cassegrain focus and the Coude focus. tin No. 5 of December 1968, which in- These focal ratios determine the dimen- The early years of ESO's project coin- cludes a summary of large telescope sions of the telescope tube. The design cided with a general, international projects under design or construction in of all other components of the project broadening of interest in large-tele- December 1967. follows from these. It has been men- scope building and the publication of Finally, as a quite useful - and tioned before (article IV) that the exam- significant documentation. In the year readable! - review of the main ele- ple ESO had in mind in the very begin- 1960 appeared the compendium "Tele- ments in large-telescope construction ning was the 3-m telescope of Lick Ob- scopes", Volume I of the series Stars and the status of the principal pro- and Stellar Systems edited by Gerard P. jects, let me mention B.V. Barlow's monograph "The Astronomical Tele- * Previous articles in this series appeared in the Kuiper and Barbara Middlehurst. It con- Messenger Nos. 54 to 60. tained chapters by leading experts, scope" of 1975 [I]. The Choice and Ordering was one of more-than-average circum- servers in the United States among of the Optics ference . . . whom especially I.S. Bowen, the Direc- The order to Corning in its final form tor of Mt. Wilson and Palomar Obser- The increase of the originally sug- was placed on January 25, 1965. The vatories, should be mentioned. At the gested diameter of the big mirror from 3 blank, made of fused Silica, was ac- first Council meeting after the ratifica- to 3.5 m (eventually 3.6 m) was one of cepted at Corning's (at Bradford, USA) tion of the Convention, in February the outcomes of the visit of Fehrenbach on February 23, 1967 in the presence 1964, Fehrenbach as Chairman of the IC and Heckmann to observatories in the of Fehrenbach, Heckmann, J. Texe- summarized the situation as follows. United States in 1961 (see article IV). reau (of the Laboratoire dlOptique of "1 - Le telescope doit comporter un Experience with the recently completed Paris Observatory) and J. Espiard of the foyer Cassegrain ouvert a F/8 qui en- Lick 3-m telescope had shown that the firm of REOSC in Ballainvilliers, France, traine une ouverture du miroir principal observers-cage at the prime focus was where the mirror was to be processed comprise entre 2,7 et 3, le foyer Coude inconveniently narrow when used by a for its final shape. The contract with ouvert a F/30. bulky observer. As, however, an in- REOSC was signed in June 1967 and 2 - Un effort particulier doit Btre fait creased diameter of the cage would the blank arrived there later that year. pour augmenter les champs de bonne block an unacceptably large part of the After it had turned out in the course of definition. - - - surface of the 3-m primary mirror for the 1968 that the blank showed certain su- 5 -- - Une combinaison du type infalling light, Heckmann and Fehren- perficial defects which required provid- Ritchey Chretien ouvert a F/3 doit per- bach suggested an increase of its ing it with a new toplayer at Corning's, it mettre d'obtenir: diameter to 3.5 m [2]. The ESO Com- was back again at REOSC in September - au foyer Cassegrain, ouvert a F/8, mittee in its meeting of November 1961 1969 for final processing. This was com- un champ plan de 30' de diametre (So- took note of this, but thought it wise not pleted two years later; in February 1972 lution de M. Kohler). yet to change the text of the Convention formal acceptance by ESO took place. - au foyer direct, un champ de lo which was still in the process of being By that time two studies of the proper- avec lentilles minces et de diametre re- approved by the governments. For the ties of the mirror had been published. lativement petit, dont une de surface time being, the formulation "un tele- One, in 1967, by J. Texereau in collab- aspherique. (Solution de M. Baranne.) scope d'environ 3 metres d'ouverture" oration with J. Espiard: "Examen du Dis- - un champ suffisant au foyer Coude." would leave the door sufficiently open que en Silice Fondue de 372 cm pour A. Baranne of Marseilles Observatory for changing the size once signing and European Southern Observatory", and and H. Kohler of Zeiss-Oberkochen, ratification would have passed. How- one, in 1971, by G. Lemaitre of Mar- mentioned here, both experts in as- ever, in the planning of the telescope, a seilles Observatory: "Sur la Flexion du tronomical optics, had been engaged in mirror diameter of 3.5 m soon became Grand Miroir de 3,60 m de European the design since the early stage of the the canonical figure, and this grew to Southern Observatory". These studies project; their studies contributed essen- 3.6 m after it had turned out later - in appeared in ESO Bulletin Nos. 2 and 8, tially to the final properties of the tele- 1967 - that the blank of 3.72 m diame- respectively. scope. Early results of their work were ter, as delivered by the manufacturer, From the very beginning, the design communicated in ESO Bulletin No. 2 of Corning, allowed a useful diameter of at for the telescope aimed at using it in the August 1967: "Le telescope de 3.50 m least 3.6 metre. In retrospect, it seems three modes: Prime, Cassegrain, and de diametre" by Baranne and "The Opti- to have been ESO's good fortune that Coude focus. Exact values of the three cal System for the 3.50 m Telescope" by one of Lick Observatory's most ardent focal ratios - F/3, F/8, F/30 - were cho- Kohler [3]. Compared to the earlier gen- observers of the 19501s,apart from be- sen by the Instrumentation Committee erations of large optical telescopes, the ing highly respected scientifically, also (IC) after consultation with various ob- ESO 3.6-m optics was designed to en-

The mirror blank for ESO's 3.6-m telescope ab,out to be delivered by Corning Glass Works. The right-hand photograph shows ESO's Director, Otto Heckmann, in discussion with a (yet unider ~tified)person of Corning's Management. The (undated) photographs were presented to ESO by Corning's. From the EHPA. The mirror blank for ESO's Large Telescope, made of fused silica, was delivered by Corning's in February 1967. The blank with total diameter of 3.72 m, of which about 3.6 m became the optically useful part, had been manufactured by fusing seven hexagonal pieces, plus the six triangular pieces to complete the circular form, as sketched in the drawing at the left. This formedpart of a study of the disk by J. Texereau and J. Espiard, published in ESO Bulletin No. 2 of August 1967 (page 39). The photograph at right, presented to ESO by Corning, shows the positioning of the central hexagonal piece in the fusing procedure in December 1968 when a superficial flaw was eliminated from the mirror. From a set of photographs by Corning's in the EHPA.

able observers to obtain photographs sibility of the TP Division about which mounting and, hence, to rapidly increas- with sharp definition of the stellar im- more will be written in the next article, ing cost of the telescope. Compensa- ages in considerably larger fields. but in the course of the preceding years tion for the residual tendency to flexure Essential in these solutions is, that just the work on the figuring and testing at of the mirror therefore was achieved by before reaching the photographic plate, REOSC had been accompanied by a a support system placed under the which is placed in the focal plane of the small group of experts on behalf of ESO, mirror which acts through the force of Prime or Cassegrain focus, the light of whom I should mention especially A. gravity. It consists, for the ESO tele- traverses a combination of lenses. By a Baranne and G. J. Monnet of Marseilles, scope, of a series of 30 concentrically suitable choice of their optical proper- D.J. Malaise of Liege, A. Behr of placed and independently acting ties, in combination with a properly cho- Gottingen and K. Bahner of Heidelberg- supports at the bottom side of the sen figure of the mirrors - a choice Konigstuhl. mirror, whereas at its sides the mirror is made possible through the new compu- supported by three pads and a system ter techniques of the 1960's - optimal of air cushions. Each of these 30 bottom The Mirror Cells optical performance could be achieved. supports is adjustable in itself but once The principle of such a combination of Between the optical system and the the telescope is in operation, the reflecting and refracting elements was telescope tube there is an important in- supports cannot be adjusted from out- known as a Ritchey-Chretien system af- terface: the mirror cells. In them, the side. ter the names of the American and mirrors are carried permanently and in The design and manufacturing of the French opticiens who developed it in such a way that deformation of their mirror cells was ordered from the firm of Paris earlier this century. The combina- shape (which would result in deteriora- REOSC that also was to do the figuring tion chosen for the ESO 3.6-m is some- tion of the stellar image) is avoided as of the mirrors. The reason is, that what is times referred to as a Modified Ritchey- much as possible. This is no small re- finally tested is the performance of the Chretien or a Quasi Ritchey-Chretien quirement if one realizes that during the combination of mirror and cell as a unit. system. motion of the telescope tube while it These combined units were delivered by For the extra reflecting components "follows" the star, the mirrors assume REOSC in 1972. employed in the Cassegrain mode (one continuously changing tilts and orienta- At the moment this article is written, it mirror) and in the Coude mode (four tions. The problem was particularly is just in this domain of telescope design mirrors), all of them sometimes referred pressing for the large primary mirror. that a revolutionary improvement has to as "secondary optics", the blanks This has, as mentioned, a diameter of been introduced: the "active optics" de- were ordered in 1966 from the firm of 372 cm, and an average thickness of scribed in the Messenger of June 1989 Heraeus-Schott in the German Federal about 50 cm and a total weight of and implemented in the New Technolo- Republic and delivered in the years 10,970 kg. (For detailed specifications gy Telescope. Modern techniques, in- 1968 and 1969. These also were made see the article by Lemaitre quoted be- cluding continuous computer control, of Silica. Their figuring was included in fore.) The mirror derives its rigidity from have made it possible to abandon en- the contract with REOSC and finished this thickness, but this is not quite suffi- tirely the idea of rigidity of a mirror as by them in the years 1970-1 972. cient. achieved by its thickness. The solution By the time of the formal acceptance On the other hand, there is a limit to towards the problem of obtaining opti- of the optical ensemble of primary and the thickness because an increase of mal performance is found by taking ad- secondary mirrors, in 1972, the Tele- weight leads to rapidly increasing vantage of a thin (and light!) mirror's scope Project had become the respon- demand on the sturdiness of tube and flexibility and steadily controlling its In (August?) 1968 the blank for the 3.6-m mirror arrived at the firm of REOSC in Ballainvilliers near Paris, for grinding and polishing towards its final shape. On the above photographs: - upper left: arrival of the mirror blank in its crate at REOSC, - upper right: the crate deposited horizontally, - lower left: wooden packing material and the iron ring holding the mirror being removed, - lower right: first hand- and foot acquaintance with the mirror by (in the foreground) Charles Fehrenbach (left) and Andre Couder (right). From a set of photographs in the EHPA.

shape by a system of numerous and ment devrait &re fait par un bureau they were influenced strongly by sug- independent, but actively, from the out- d'etudes independant, acceptant un gestions of Strewinski. side adjusted supports. Twenty-five marche d'etude." It confirmed the early Strewinski's design deviated in sever- years ago, when Heckmann and his intention of the ESO Committee to cre- al important respects from that of large associates searched for the best ate a design bureau. In May of that year telescopes then in operation. First, note support system for the ESO 3.6-m, this it had become clear that of the two that the whole concept was still based was undreamt of. . . engineers whose collaboration in the on the classical model of a telescope project was hoped for, the work for the moving around a polar axis (which is large telescope would mostly involve directed towards the celestial pole) and Tube and Mounting; Strewinski's Strewinski. According to Heckmann's the declination axis, perpendicular to Pre-Design report at the June 1965 Council meet- this. Of these two motions, only the first Fehrenbach's summary of the recom- ing, a draft contract with the engineering (and uniform) one is required during the mendations of the IC by the time of the bureau of Strewinski had been drawn up telescope's following a star during ob- first Council meeting, in February 1964, (but it is not clear whether it was ever servation. The radically different azi- also contained the following statement: signed). Ideas about the nature of the muthal design now employed for large "L'etude de la mecanique de I'instru- design were shaped within the IC, but optical telescopes was in use at that Shaping and testing the mirror at REOSC. Left: grinding the mirror (the large "white" disk) by means of the (smaller) rotating disk touching the upper surface of the disk. Among the spectators, the Director of REOSC, M. Bayle (in dark jacket in front of the group at right). Right photograph: the optical laboratory of REOSC at which the shape of the mirror was tested. In order to do this with the mirror in horizontal position, REOSC built the high "optical tower" at right in the picture. From a set of photographs provided by REOSC in the EHPA. time only for large radio telescopes, and respect to the horizon. An impression of horse-shoe disk. By this construction it was planned for (and later realized in) the weight we are dealing with may be the diameter of the horse-shoe could be the 6-m USSR optical telescope in the obtained from the minutes of the 28th diminished to less than 8 metres. For the early 1960's. meeting of the IC, of May 1969, when upper (horse-shoe) bearing Strewinski One of Strewinski's innovations con- the tube including the optics was esti- chose an oil bearing, the sliding surface cerned the storage of the optical ele- mated to weigh about 60 tons. of which is supported on two fixed ments which are alternately used for the A different concept had been adopted pedestals, and in Strewinski's design different modes of operation. Whereas, for the Kitt Peak 150-inch telescope. the centre of gravity of the movable for instance, at the 200-inch Palomar Here, the bearings carrying the ex- parts of the telescope is vertically above telescope those optical elements, which tremes of the declination axis rest in a the midpoint of the line joining these two are not in use during operation in a very sturdy horse-shoe which in itself oil pads. Oil is constantly pumped at particular mode, remain stored within forms the upper bearing of the polar high pressure into the two sliding sur- the telescope tube, Strewinski pro- axis. Even without detailed knowledge faces, so that during the operation the posed for the ESO telescope separate of the forces acting on the bearing, one telescope floates on two thin films of oil. top ends of the tube carrying the differ- senses that for a heavy telescopes tube The sliding surfaces of this upper bear- ent secondary mirrors, so that those not such a design is more suitable than a ing were given a spherical shape, a con- in use could be parked outside the tube fork mounting. A solution like this was cept Strewinski had earlier introduced in quickly interchangeable manner. An considered by Strewinski also for the for the Schmidt telescope of Hamburg advantage of this solution was a reduc- ESO telescope. However, he rejected it Observatory. tion of the weight of the tube, and in order to avoid the large diameter Once these principal design charac- hence, simplification of the design and which would have been required for the teristics had been agreed upon - and reduced costs of the mounting. horse-shoe, about 12 m. As Ramberg we do recognize them in the 3.6-m tele- Another aspect of Strewinski's design explained in his presentation of scope as it has ultimately been realized was the combination of horse-shoe and Strewinski's design at the April 1965 - many details had to be worked out in fork mounting. In the classical mount- IAU Symposium, Strewinski feared "that close consultation between the bureau ing, realized, for instance, in the Lick it will be a fairly complicated matter, of Strewinski, the Directorate and the IC 120-inch and also in the ESO I-m and after having manufactured such a disk in and its subcommittees. They met fre- many other telescopes, the extremes of Europe, to transport it to Chile and then quently in the year 1966 and thereafter. the declination axis rest in the extremes take it up to the top of La Silla - - -" [4], This led to the so-called pre-design of the two prongs of a fork which forms and Ramberg mentioned this also at the studies and drawings in which specific an extension of the polar axis. For large December 1965 meeting of the IC. solutions were formulated for the vari- telescope tubes, the top end of the fork ous technical problems encountered. which carries all the weight of the tube The Combined Horse-Shoe and Next should follow the exact designs required for the construction when the including the optical elements, is rather Fork Mounting distant from the upper bearing of the project would be in the hands of the polar axis, particularly so if the fork is This led Strewinski to his compromise manufacturer. made long in order to leave room for solution: the combined horse-shoe and bulky equipment at the Cassegrain fork mounting. It is demonstrated in the Stagnation and Growing accompanying drawing, taken from the - focus. This implies high demands on the Impatience svstem of bearinas of the polar axis, and presentation in the 1965 Symposium in the case of the ESO telescope espe- keport. Here, the declinatidn axis is These pre-design studies and draw- cially so because at La Silla the axis supported by two relatively short and ings were, however, produced at unex- makes an angle of 29 degrees only with very strong fork prongs mounted on the pectedly low rate by Strewinski's A sketch of the design of the 3-m telescope of Lick Observatory. In 1953, Walter Baade suggested that the principal telescope for the European Southern Observatory should be a copy of this telescope, which became operational soon afterwards. ~h;sketch shows the ~i~k3-,77telescope when its mounting was virtually complete, in telescope tube with its primary mirror of 3 metres 2nd secondary November 1954. The lower part of the telescope tube is shown, mirrors for operation in the Cassegrain and Coude modes. For hanging on the declination at the top end of its long fork, the motion in declination, the telescope tube rotates around an axis arms of which are about 7 metres long, The of the tube which is mounted at the top end of two long fork prongs; the fork including the optics is about 40 tons (whereas the estimated weight forming the extension of the polar axis. for the ESO 3.6-m tube and optics was about 60 tons). From: Sky and Telescope, March 1955, p. 176. From: Sky and Telescope, May 1955, p. 272.

The engineer W. Strewinski (extreme left) visiting Observatoire de Haute-Provence in May 1966 with the ESO Instrumentation Committee and other specialists. From left to right next to Strewinski: Ch. Fehrenbach, 0. Heckmann, a collaborator of Fehrenbach, A. Behr, A. Couder, M. Migeotte, and A. Baranne. Main features of the mechanical design of ESO's 3.6-m telescope and Schmidt telescope are due to Strewinski who had been engaged by ESO since soon after its creation. Early in the 1970's the ESO TP Division at Geneva took over for the realization of the 3.6-m telescope, as will be described in article IX; for the completion of the Schmidt telescope see article X. The photograph was taken on the roof of the Spectrographic Telescope Building-in-construction at Haute-Provence Observatory. Photograph in envelope marked "Spectrographic Telescope" in the EHPA. The 5-m Hale telescope of Palomar Mountain, shown here, had been The 4-m Mayall telescope of Kitt Peak Observatory, which came into in regular operation for four years when first talks about the creation regular operation in 1974 after its creation had been initiated in the of ESO took place in 1953. Its realization had taken many years due early 1960's by AURA. As in the case of the 5-m Hale telescope, the to interruption by World War 11. The declination axis is positioned north bearing of the polar axis has the shape of a horse-shoe, but about half way between the south and north bearings of the polar now the declination axis lies in the plane of the horse-shoe. This axis so that the weight of telescope tube and polar axis is devided solution was considered for the ESO telescope, too, by Strewinski, over the two bearings. The horse-shoe shape of the north bearing but he preferred the solution described below in order to avoid the allows the telescope to observe objects near the north pole. large diameter of the horse-shoe. From Sky and Telescope, January 1973, p. 14.

bureau. The Directorate, especially lent, the capacity of his bureau is evi- The IC Meetings in 1969 Heckmann, in first instance kept full dently too small - - -. A solution would confidence in Strewinski to handle the be to give the main part of the definitive The meeting in January 1969 was al- task, but doubts began to grow among design to a large firm which then could most entirely devoted to the design of the IC and Council when a year after the work under the supervision of Strewins- the telescope tube. ltems discussed Large Telescope symposium little pro- ki. " However, suggestions to give part of were: technical solutions for the secon- gress was evident. In his report at the the pre-design to an outside firm met dary mirror exchange when the observer Council Meeting of April 1966 in San- strong opposition from the part of Heck- changes his mode of observing; the sta- tiago (following the dedication of the mann, who emphasized "that the pre- bility of the position of the primary mirror road on La Silla), Fehrenbach felt com- design forms a unit; - - - It would be a during exchange of top parts of the pelled to state: considerable loss of time to give the tube, when the mirror is in vertical posi- "I1 faut considerer que I'etude du task - - - to another firm, because no tion; the interchange of equipment used grand telescope est arrivee au stade ou firm exists holding something like at the prime focus; the design of the il est necessaire de penser a sa realisa- Strewinski's specific knowledge on the mirror supports; specifications and de- tion dans un delai raisonnable. Un cer- subject. " sign of the Cassegrain cage; and the tain nombre de membres de la C.I. Again a year later, in the July 1968 design of the drive system. ltems taken m'ont indique, en prive, leur inquietude meeting of Council, Fehrenbach on be- up in May 1969 were: the (very impor- concernant la methode proposee. half of the IC reported that Strewinski tant!) question of the flexure of the fork D'apres des informations, nos colle- was supposed to deliver the complete prongs in different positions of the tube; gues americains prevoient un bureau pre-design, drawings and descriptions, the design of the south (upper) bearing d'etudes de 50 ingenieurs et techni- before June 1, 1968 but that this had and the safeguard against earthquakes; ciens, travaillant pendant plusieurs been delayed due to the necessity for the choice of the (mechanical?) drive annees pour I'etude complete de leur Strewinski to enter deeply into parts of system; the control of "mirror 5" of the telescope de 3,75 m a Kitt Peak. I1 est the definitive design . . . In fact, the first Coude system. certain que I'organisation prevue par part consisting of 34 drawings, mainly During the second part of this meet- nous, c'est a dire un bureau d'etude related to the telescope tube, was deliv- ing, a small ad-hoc group consisting of reduit, par ailleurs charge de /'etude du ered only in November 1968 and exten- Stromgren (as Chairman), Fehrenbach, telescope de Schmidt, ne permet pas sively discussed by the IC in January Heckmann, Ramberg and Strewinski une realisation dans un delai accep- 1969, whereas the second part, also 34 convened separately. It subsequently table. Je me demande s'il ne vaudrait drawings, for the telescope mounting, reported to have found Strewinski's pre- pas mieux passer la commande de la was delivered in May 1969 and discus- design sufficiently advanced that pre- mecanique a une firme privee, le bureau sed by the IC in May and June 1969. As liminary steps might be taken towards d'etude de M. Strewinski restant organe these three meetings were the last ones the implementation of the project, and it de liaison entre cette firme et la C. I." of the IC before the policy of Council suggested names of firms to approach Concern about the lack of progress was radically changed, and the creation for first contacts. Strewinski would be in the pre-design continued to be ex- of the Telescope Project Division of ESO supposed to continue the detailed de- pressed at meetings of Council and IC. was on the horizon -the IC would meet sign work but should rather not be in- A year later, at the June 1967 meeting of again only a year later, in June 1970 -, volved in shop-drawings unless he Council, it was agreed that "although let me briefly describe the proceedings would increase his staff by 10 to 15 the quality of Strewinski's work is excel- of those IC meetings in 1969. engineers and draftsmen. A time the telescope and its auxiliary equip- ment such as spectrographs, and part B supporting first of all the heavy rotating dome, but also serving for electronic laboratories, dark rooms, storage space, laboratories, aluminizing facili- ties, air conditioning, elevators, etc. Reason for this separation of structures is that no vibrations caused by the ac- tivities in part B should be transmitted to the telescope and its auxiliaries of part A (for instance those caused by the rota- tion of the dome). An important feature of structure A for the 3.6-m Telescope was a large floor below the observing deck for the erec- tion of the Coude spectrographs; these, together with the size of the dome, be- The design for the ESO 3.6-m telescope as presented by Strewinski at IAU Symposium No. 27 came the determining factor for the hori- on "The Construction of Large Telescopes" in April 1965. In order to reduce both the length of zontal extension of the building. A the fork arms as required for the Lick 3-m telescope design, and the large diameter of the length of 24 metres for the Coude light horse-shoe as realized in the case of the Kitt Peak 4-m telescope, Strewinski proposed the combined fork and horse-shoe solution shown here, Another feature of his solution was a path figured in early planning, but was spherical shape for the horse-shoe bearing, and positioning the centre of gravity of telescope reduced to 18 m at most by November plus polar axis vertically above the line joining the two oil pads which carry this bearing. 1966. The diameter of the dome was From The Construction of Large Telescopes, IAU Symp. No. 27, Ed. D. L. Crawford, 1966, estimated to be 28 metres [7]. Through- p. 118. out the designing by Lenz, the result of the special requirements for the Coude floor was a building of rectangular schedule was proposed for the ordering As described in my previous article, shape which risked to have a deteriorat- of parts: for the period October 1969 to around this time - the middle of 1969 -, ing effect on the image quality in the April 1970 these should include the main dissatisfaction about the lack of pro- telescope. parts of the mounting, and subsequent- gress was one of the reasons for creat- Another basic measure was, of ly, until October 1970, the main parts of ing the Working Group of Alline, Funke course, the height of the telescope the telescope tube. In a third period, and Scheidemann. A worried Council above ground level. This was defined as until April 1971, the ordering of the tele- considered alternative ways to realize the height of the crossing point of decli- scope drive and mirror support systems the telescope, and the role of Strewins- nation axis and polar axis, and fixed at were foreseen. Presupposition would be ki's bureau was more and more con- 24 metres. The decision to put the tele- that Strewinski would settle for this fined to the completion of the Schmidt scope that high goes back to the results time-schedule contract. Strewinski him- telescope. We shall come back to the of measures of image quality at different self recommended collaboration with a Schmidt in article X, and before entering heights above ground level by the local firm. the description of the new approach in method of Siedentopf described in arti- However, doubts were expressed - the 3.6-m telescope project, review cle II, for which data had been obtained particularly from the part of S. Laustsen what had been done on the design of by Andre Muller over a long period by (about whose role in the project we will the telescope building and dome and in means of high masts, one of which was see more below) - whether the time the field of automation. erected at the highest summit of La schedule was realistic: "An efficient Silla. Note that it was this element, the group of astronomers and engineers is required image quality, that determined The Building necessary for the planning and coordi- the height of the building, not the need nation of the whole 3.6-m project and Once the main properties of the tele- of space for housing the various for the design studies and development scope had been fixed, steps were taken facilities. work bearing on control and automa- toward the design of building and dome. Of the many other aspects of the de- tion " [5]. At its November 1966 meeting, Council, sign, let me mention only the important In the June meeting, four weeks later, at Heckmann's request, agreed that this problem of providing proper heat insula- aspects of the design of the Cassegrain project should be handled separately tion in order to avoid heating up of the cage and the Coude mirror system were from the building projects of the first inside of the dome during day time. reviewed, after which Heckmann global- stage of which we described the dedi- In the July 1968 meeting of Council, ly summarized still pending matters: cation in article VI. In order to allow Ramberg could report that the firm of mounting of the Coude mirror; Casse- close consultation, a civil engineering Lenz expected to finish the pre-design grain cage; facilities for optical adjust- firm in Hamburg was chosen, Lenz Ar- by the end of that month, and in the ments; mirror support systems; prime chitekten & Ingenieure. Their architect December meeting first steps for a focus correctors and plate holders; drive Mr. Mix gave a first report at the IC building contract were discussed. How- system; encoders; computer control in- meeting of December 19, 1967. From ever, the delay in the design of the tele- terface. However, no decision was ta- the minutes of this meeting [6] main scope kept Council and Directorate ken with regard to a recommendation to features of the design can be inferred, from taking this further step towards Council for entering contacts with con- but unfortunately no drawings have so realization. Coordination of construction struction firms as had been suggested far been located in the ESO files. A basic activities on La Silla with those for the at the May meeting. A next meeting of feature of such a telescope building is building of the 4-m telescope on Cerro the IC was scheduled for October 1, its consisting of two parts on separate Tololo was discussed with AURA in 1969, but not held. foundations: part A for the support of Santiago in March 1969 [8]. The Dome Simultaneously with the planning of the building, preparations were made for the design of the dome. Favourable experience had been gained with the firm Seibert-Secometal at Saarbrijcken, that had provided the domes for the first construction phase. This early work had been supervised by their engineer W. Bauersachs, who has described it in ESO Bulletin No. 4 of July 1968 (and who years later joined the staff of ESO). Hence, this firm was now also charged with the design and construction of the dome for the 3.6-m telescope. This was finished by the end of 1968, and so this project, too, was ready for tendering in 1969.

The drawing reproduced here is part of a set of drawings made by the bureau of the engineer Automation in Telescope Control Dr. W. Strewinski and marked "Gesamtanordnung" and "Stand 18- 10- 1968". This set of Among the many valuable ex- drawings was reproduced in Document Cou-59, written by ESO's Technical Director J. periences of Fehrenbach and Heck- Ramberg for the Council meeting of December 1969 and entitled "The Present State of the 3.6 m Telescope Project". This section of the drawings shows the arrangement proposed by mann during their visit to observatories Strewinski for the storage of the different top-ends of the telescope tube which carry the in the United States in 1962 was the secondary mirrors for use in different modes of operation. confrontation with new, electronic com- The proposal led to the more detailed design by the TP Division shown in the sketch below. We puter techniques for the control of tele- also note, albeit vaguely, in this drawing the square contour of the telescope building scope functions. This rapidly developing extending beyond the projection of the dome, a design that followed from the large space that field was also energetically pursued in was deemed necessary for the long optical paths in the Coude spectrographic equipment. The the ESO member states and led to a design of the final, cylindrical, telescope building on La Silla represents a radical change, document "Some Suggestions for Auto- introduced in the early 1970's. mation of the 3.6-m Telescope" issued by the ESO Directorate in ~ebruar~1968 under supervision of the Technical Di- rector Joran Ramberg [9]. The authors included two young astronomers, F. Dossin of Liege who had joined the office of the Director in February 1966, and S. Laustsen of Copenhagen Obser- vatory who acted as consultant to the Directorate. Main functions of the automation as listed in the document and elaborated in detail were: A) Automatic Control: set- ting of the instrument, telescope driving, dome and shutter operation, setting and driving of siderostate, and "local driv- ing", and B) Semi-automatic operations (push-button control). The new con- cepts were discussed in a series of meetings: in February 1968 in Paris, in September 1968 in Karlsruhe at the firm of Siemens (in view of a collaborative project with this firm) [lo], and at the IC meetings of November 1968, and May and June 1969. Meanwhile, Svend Laustsen had be- come a staff member of ESO per Sep- tember 1968, in order to assist the Di- rectorate in matters of automation of telescope operation and for the de- velopment of a programme for auxiliary both also from Denmark. It continued to the Schmidt, as we saw in article IV, instrumentation for the 3.6-m telescope. grow in 1970 and would become the could be identified with the specific in- Gradually, an in-house working group nucleus of the 3.6-m Telescope Divi- terests of institutes in the Netherlands, was formed headed by Laustsen, which sion, the creation of which we shall de- France and the German Federal Repub- by the end of 1969 also included the scribe in the next article. lic, respectively, it now had become astronomical technician B. Malm and Whereas in the early phase of ESO, Denmark's turn by providing this nu- the electronics engineer M. Blichfeldt, the three telescopes, 1-m, 1.5-m, and cleus. 35 References and Notes Kosmos, Weltmodelle, Verlag Piper and Co., [5] FHA, Minutes 28th meeting of the IC, Abbreviations used: Munchen-Zurich, 1976. p. 911 0. EHA = ESO Historical Archives (see The [I] Wykeham Publications Ltd., Lon- [GI FHA, DOC.IC-26 = BG-16. Messenger of December 1988). don- Winchester 1975. [7] FHA, DOC.IC-18 = BG-15. FHA = Files Head of Administration at ESO [2] Heckmann Sterne, p. 323. [8] FHA, Minutes of the 12th Cou Meeting, Headquarters. [3] For reports on work by Baranne, Kohler, p. 13. EHPA = ESO Historical Photographs Ar- and Paul of the years 1962 and 1963, [9] FHA, DOC.IC-24. chives. see EHA-I.C.l.9.m. [lo] For reports of these meetings, see FHA Heckmann Sterne = 0. Heckmann, Sterne, [4] See page 118 of the Symposium Report. Docs. IC-27 and IC-29.

Observations of Visual Double Stars at La Silla M. SCARDIA, Osservatorio Astronomico di Brera, Merate, Italy

Introduction This enormous task of observation Of the many types of observing pro- has led to the discovery of over 70,000 grammes made at La Silla with the most double visual stars in the entire sky, of sophisticated equipment provided by which about 900 have today a known modern techniques, one in particular orbit. distinguishes itself because it utilizes for The history of the visual double star the observations only the human eye, astronomy is a fascinating chapter in the the oldest and most traditional of detec- history of Astronomy; for those who tors used in astronomy. This research is would like to examine it more closely, the micrometric observation of visual there are many articles and books that double stars. deal with it in detail (Baize, 1930 - The concept of a visual double star is Heintz, 1978 - Couteau, 1988). a relative one: by a visual double star we mean the whole of two or more stars, angularly close, which can be distin- The Method Figure 1: Scheme of a filar micrometer: A and guished from each other through the B are fixed wires, while C is the mobile wire eyepiece of the telescope. It is then The first "modern" measurements, by quality and accuracy, date back to whose movement is commanded by the rota- evident that, when increasing the tion of the micrometric screw. diameter of the telescope, ever more 1828, and were made by F. G. W. Struve narrow double stars should become vis- who used a refractor with a diameter of ible as distinct objects. However, there 24 cm at Dorpat in Esthonia. It was built exists a lower limit, introduced by the by J. Fraunhofer and was at the time the the origin the "main" star (usually the earth's atmosphere, which is of the or- greatest and the first conceptually mod- brightest) (Fig. 2); der of O'il. This limit to visual observa- ern instrument in the world. Struve dis- (c) the separation @ between the two tions can sometimes be overcome by covered and measured 3134 double stars, expressed in arcsec (Fig. 3). For observers of great experience, on sites stars on the basis of a specific research this it is necessary to know the scale of of particularly good seeing (Couteau, programme. the instrument in arcsec/mm. 1987). We also owe to Struve the method of The astronomy of visual double stars measurement of separations with the is by now over two centuries old. In filar micrometer, known as the double 1778, W. Herschel, following one of distance method, commonly utilized Galilee's ideas, began systematic ob- even nowadays. The filar micrometer servations of visual double stars with (utilized for over 80 % of visual measure- the purpose of determining stellar par- ments) is a very simple instrument: it is allaxes. He did not manage, com- made up of a reticle of spider threads, prehensibly, to determine any parallax, placed in the focal plane of the tele- because the quantities to be measured scope, two of which are fixed and per- were too small for the coarse microme- pendicular to each other. The third is ters of that period, but in 1803, with a mobile (by means of a micrometric publication that has made history (Her- screw) and is parallel to one of the fixed schel, 1803), he proved that physical lines. The entire device can rotate binary stars were a reality and that the around the optical axis of the telescope law of universal gravitation was valid (Fig. 1). also outside the solar system. The measurement of a visual double More than 600 astronomers after star consists in the determination of Herschel have measured visual double three fundamental parameters: Figure 2: The measure of the position angle 6 stars with various techniques, leaving a (a) the date of observation expressed is made by rotating the micrometer around the optical axis of the instrument so that the patrimony of about 1,000,000 individual in years and decimal fraction; fixed wire A bisects the two stars S1 and 52. measurements, summarized for practi- (b) the position angle 6, or the angle The most luminous star S 1 is, by custom, cal purposes in over 410,000 annual between the line that connects the two considered the principal star and is chosen averages. stars and the north direction, taking as as the origin of the coordinates. The Precision obtain the orbital elements of a binary star, even only relatively reliable, it is The best instrument for this kind of necessary to observe at least half of its high resolution observations is the tradi- orbit. Hence the necessity for systema- tional refractor, which was very com- tic and continuous observations and for mon throughout the last century. Its long a new generation to take the place of focus allows high magnification factors, each generation of observers that which are essential in order to clearly passes. The astronomy of double stars examine the diffraction image provided is the branch of astronomy in which the by the lens. Experience teaches that an ties between past, present and future magnification which is 3-4 times the are the closest. Today we are able to resolving magnification (the minimum calculate an orbit only because earlier magnification needed to see the diffrac- generations of astronomers have ob- tion image at the limit of visual acuity) is served this star, and similarly our obser- sufficient for this purpose. Also reflec- vations will be indispensable for the as- tors are currently used for such obser- tronomers of the future. The unrelenting vations, but their use is more delicate flow of time, instead of condemning because of the obstruction by the sec- these measurements to oblivion, makes ondary mirror, of the less stable focus them precious and indispensable. and of the higher sensibility to the air It could be objected that astronomers turbulence. don't have the patience to wait all this The precision which a good double time to obtain more information about star observer can reach is considerable; stellar masses, and that a sensible if the observing conditions are optimal, choice of the systems to be observed he can measure the separation of a could shorten the waiting time. The large double star or estimate the one of problem has been dealt with and it has a very narrow double (below the resolv- been proved (Couteau, 1978), on the ing power of the instrument used) with basis of a hypothesis about the work an uncertainty of only a few hundredth which is very close to reality, that the of an arcsec. For the position angle, the rapidity with which information on matter is different, because the uncer- masses can be obtained, grows as tainty depends on the separation: from a where D = diameter of the instrument. few tenths of a degree for a well sepa- The large apertures allow the observa- Figure 3: The double distance method. To rated double star, to few degrees in tion of narrower doubles, which have measure the separation, the micrometer is case of a double star whose separation a higher probability of being short- rotated in such a way that the fixed wire A is just a bit more than half the resolving period binaries and therefore give us and the mobile wire C are perpendicular to power of the objective used. In these the line S 1-52, By means of the fine motion information on their masses in few de- conditions he will not see two distinct cades. of the instrument the fixed wire A is superim- images anymore; the double star will posed exactly on the star S 1 and by moving New techniques of observation, like appear like a slightly oval image (Fig. 4). the micrometric screw the mobile wire C is the speckle interferometry, were im- brought to bisect the star S2 and a first The final purpose of the observation plemented during the last twenty years, reading of the micrometric screw is done. of visual double stars is the calculation but are still little used. The potential of The operation is then repeated, bringing the of the orbital elements which, once this technique, which was introduced by fixed wire over the star S2 and the mobile known by means of the third law of A. Labeyrie (Labeyrie, 1970) is great, one over S 1. The difference between the two Kepler, make it possible (if the parallax especially for the very narrow double readings (Zd), expressed in fractions of a is known) to determine the sum of the millimetre, multiplied by the scale of the in- stars (Q < O'!2), where the efficiency and masses of the system. the precision of the visual observation strument expressed in arcsec/mm, gives us The visual double stars, in conclusion, the double of the distance (Q) between the are lower. However, it is rather compli- two stars in arcsec. are indispensable for the determination cated and, for the time being, quite ex- of stellar masses, this fundamental pa- pensive in men and material, which is rameter of astrophysics, which other the opposite of the visual observation types of binary known are not able to provide, except in particular cases. Few astronomers are aware of how modest the number of the accurately measured An estimate of the difference in mag- masses really is. The astronomical com- nitude between the two stars is often munity usually uses the mass-luminosity added to these main quantities. Some relationship, but this empirical law is brief comments on the measurement obtained experimentally starting from a (the difficulty, the aspect of the couple, few dozens of masses known. the state of the seeing, etc.) may be useful later, for a possible weighting. An essential condition however is that the Figure 4: The aspect of a double visual star seeing must be good. The Patience for different values of the distance between "To measure well, you must see well": the components. The distance is expressed this principle, always valid, by Otto The observation of visual double stars in function of the radius of the first dark ring Struve, son of F. G.W. Struve and like necessarily implies long periods of time, of the diffraction image (r = 1.22 A/D). his father a great observer of double because the huge majority of them has 0.5 0.75 1.0 1.25 stars, should never be forgotten by ob- periods of hundreds, thousands and 2.25 2.0 1.75 1.5 servers of visual double stars. even tens of thousands of years. To (taken from "Lunettes et Telescopes"). whose cost and complexity are very low. A comparison between the speckle measurements and the visual ones shows that they match very well, espe- cially in the position angle (which is the most important parameter for the calcu- lation of the orbital elements). However, as far as the separation is concerned, one sometimes gets the impression that the speckle measurements are sys- tematically shorter than the visual ones, which on the whole, nevertheless, appear to have a higher dispersion. The observers of double stars are becoming progressively rarer: their number can al- ready be counted on our fingertips. This speciality, which requires years of tough apprenticeship, suffers from the dis- affection of the young who, dazzled by astrophysics, prefer theoretical re- Figure 5: Percentage of the measurements ma de at La Silla for each class of separation. searches or shorter, experimental ones requiring less observing engagement, which are able to offer secure funds and and extremely reliable. This means no tially a filter OG 530 had been used). In fast careers, because it is "fashionable". time wasted because of instrumental this way the troublesome blue halo The indifference and, sometimes, the breakdowns. Second, the GPO is rela- around the bright stars which makes incomprehension of the astronomical tively little requested by the European difficult the observation of fainter com- community also contributes to making astronomical community; it is therefore panions has been considerably re- the work of the few who still devote possible to obtain a reasonable number duced. The mounting, because of the themselves with passion to this type of of nights in each observing period, thus position of the finder, prevents observa- research more difficult. optimizing the relative number of mea- tion south of 6 = -70°, and the obser- surements/cost of the mission. vation of objects near zenith is rather Small changes have been necessary uncomfortable, because of the insuffi- Observations at La Silla to adapt the GPO astrograph to the cient distance between the eyepiece The southern hemisphere, which in visual observation of double stars. The and the floor of the dome. The ninth the first half of this century was in a correcting lens for astigmatism near the magnitude is the limit at which stars can leading position, owing to the energetic focal plane has been removed, because be observed with reliability. But in spite activity of some great observers like In- the observations are made on the opti- of these restrictions, thousands of nes, Finsen, Van den Bos, Rossiter, etc., cal axis. The original focal length, which doubles of every separation are acces- has been suffering for many years of is only 4 metres, has been increased to sible for observation. The diffraction im- complete neglect, because no as- 9.5 metres, with a barlow lens; the ex- age provided by the lens is of good tronomer is permanently observing any amination of the image is made with a quality: it presents itself round and with- double star there, and the survey of the magnification of 760 times (4 times out defects. The observing programme southern sky relies on the observing the resolving magnification). It was foresees the observation of all the dou- activity of only three astronomers, two necessary to correct the chromatism of ble stars, orbital and not, which satis- North-Americans, Heintz and Worley, the objective, which has the minimum of fy the following conditions: (1) 6 < O0, and the writer, the only European. the secondary spectrum close to (2) m < 9, (3) 0!'18 < @ < 5V5. Only a few months ago the working 4300 A, instead of the traditional Each measurement of the position group C. H.A. R.A. from Atlanta 5600 A, with a yellow filter GG 495 (ini- angle is an average of 8 or more set- (U.S.A.), headed by H. McAlister, began to observe the double stars of the southern sky, using the 4-m telescope of Cerro Tololo and speckle interferom- etry. At La Silla, the systematic observation of visual double stars of the southern sky began in 1986. The choice of the instrument fell on the GPO astrograph for very simple reasons: First, the GPO is a refractor with a diameter of 38 cm, whose limit of observation is close to O'i18. Its diameter, which is not very large, guarantees a good result, be- cause it is hardly affected by the air turbulence; therefore, there is a high probability of having a good number of utilizable nights during each observing mission. It represents an excellent com- promise between resolution power and Figure 6: Orbit of the binary star BU 738 (P = 305 years) obtained, utilizing also the yield. It is a simple instrument, robust measurements made at La Silla in the last few years. tings, while each measurement of sep- Up till now, a total of 1840 measure- tifically valid, and which has lost none of aration is an average of 4 measures of ments of 432 systems, down to separa- its reasons of existence. the double distance. tions of 01.'18, have been made at La It is possible now, after nearly four Silla. Figure 5 shows the histogram of years and seven observing missions at the percentages of the measurements References La Silla, to make the first conclusions on made by class of separation. Baize, P., 1930, L'Astronomie 44, 268. the work done. From these first results, it is my firm Couteau, P., 1978, L'observation des etoiles Regarding the air tranquillity, La Silla belief that La Silla is a very valid site for doubles visuelles, Flammarion, Paris. is largely superior to the average of the observation of visual double stars. Couteau, P., 1987, Astron. Astrophys. Suppl. European sites of which I have direct The contribution that a good observer Ser. 70, 193. observing experience. 51 % of the (who could rely full time, for this kind of Couteau, P., 1988, Ces astronomes fous du nights have been completely utilizable observations, on the GPO astrograph, ciel, Edisud, Aix-en-Provence. or in part (26% "good quality" nights or on an instrument of superior class) Danjon, A., Couder, A., 1935, Lunettes et telescopes, Editions de la Revue d'optique and 25% "sufficient quality" nights), could give to the astronomy of visual Theorique et Instrumentale, Paris. while during the remaining 49% of double stars and to the knowledge of Heintz, W.D., 1978, Double Stars, Reidel nights, bad seeing or covered sky have stellar masses, would be fundamental. Publ. Company, Dordrecht. prevented the observations. A compari- Herschel, W., 1803, Account of changes . . . son with the seeing measurements A Final Plea in the relative situation of double stars, made at Cerro Vizcachas has allowed to Philos. Transactions, II part. establish that, when the value measured It is exactly because of the validity of Labeyrie, A,, 1970, Astron. Astrophys. 6, 85. there is better than 0'!7, generally, the the arguments exposed above that the Scardia, M., 1989, Astrophys. Journ. Suppl. images at the GPO can be considered voices heard in recent times "on the arid Ser. 71, 647. Struve, F.G. W., 1837, Stellarum duplicium et good; in these conditions the diffraction mountain" regarding the future of the multiplicium mensurae micrometricae . . ., image presents itself as stable and the small instruments are a cause of worry. Typographia Acadernica, Petropoli. "turbulence" is less than 0V14 (for the They contribute to make even more un- Texereau, J., 1961, La construction du tele- definition of "turbulence", see Danjon certain the future of this branch of as- scope d'amateur, Societe Astronomique and Couder, 1935, or Texereau, 1958). tronomy with great traditions, still scien- de France, Paris.

Long-term Photometry of Herbig AeIBe Stars in the Stromgren System P. S. THE and E. 5/50,Astronomical Institute "Anton Pannekoek", University of Amsterdam, the Netherlands

Stromgren's system and is done with some time a star turned out to be non- Introduction the small ESO telescopes at La Silla. variable we have discontinued observa- Our working group on the study of Since the magnitude limit for accurate tions of it. The study of Herbig Ae/Be Herbigt Ae/Be stars has joined Ster- measurements is about 9, in this long- stars, which usually are varying irregu- kens group of Long-term Photometry of term photometry we have monitored larly, is done for giving a better explana- Variables from the beginning on. The only the brighter 27 members of the tion of the complex problems con- photoelectric photometry is based on Herbig Ae/Be stellar group. When after nected with the variability of these ob-

too-

2.00.

AY O0

L.00 &, > 0.05

Ab-4T5[:%0.25 -[ "' ""Yq!% 0.55' 50jo 6000 '6070 6700 6300 6L20 6L50 6480 7450 7~80 7810 7840 i<7880

Figure 1: The light curve of UX Ori. The star remains quite a long time at maximum brightness, but can leave it, and stay many days close to its minimum brightness. Ay 1.8 w~~4y-~~~-~vf-T~TY CrA 200.-

QSL rb-Ay 0.36 as2!:@ ! v':; :! p!i N{ 0.38.- 4 !! 5260 5570' 5600 5070 6000 6670 6700 7070 70LO 7070 7750 7780 710 -78.40 JD-2LL0000 Figure 2: The light curve of TY CrA. There are fewer observations compared to those of UX Ori, but from the figure it is clear that the star remains close to its brightness level all the time, with sudden changes to lower brightness. jects. We have in mind the study of three example of a star exhibiting such a be- (1 989). By using a stronger code on the problems, explained further below, haviour quite strongly is UX Ori, as data used by Baade and on those ob- which can only be done with long-term shown in Figure 3. tained by the long-term photometry photometry on the same photometric There are several mechanisms pro- (spanning in total a time interval of about system. posed to explain this behaviour (Zajtse- 7 years), we have found in addition a va, 1986, Pugach, 1981, Grinin, 1988), quasi-period of about 110 days. An ex- Type of Variability, and its but no one adequately explains the ob- planation for this behaviour is still Correlation with Spectral Type served phenomena. A revised mechan- lacking. and Spectroscopic Variations ism for Grinin's (1988) explanation of the This study is made in collaboration long-term photometric behaviour of UX with M. R. Perez and J. R. Webb. The first purpose of the long-term Ori is reported in a recent paper by Bibo photometry of Herbig Ae/Be stars is the and The (1990). References determination of the shape of the light Baade, D., Stahl, 0.: 1989, Astron. Astro- curve and the range in brightness. Light Periodicity in the Light Variations phys. 209, 255. curves of UX Ori and TY CrA are shown Bibo, E., The, P. S.: 1990, Astron. Astrophys., in Figures 1 and 2 as examples. It is then Although apparently irregular, it in press. important to know whether the type of seems that in the light variations of Her- Blondel, P.F.C., Tjin A Djie, H.R.E., The, variability and/or the brightness am- big Ae/Be stars, there are quasi- P. S.: 1989, Astron. Astrophys. 80, 11 5. plitude has some relation with the spec- periodicities. These are perhaps caused Grinin, V. P.: 1988, Sov. Astron. Lett. 14, 27. Pugach, A.F.: 1981, Astroph. 17, 47. tral type and luminosity of the star. In by periodic variations in the characteris- Tjin A Djie, H. R. E., The, P.S., Andersen, J., other words, do they depend on the tics of the stellar atmospheres. Such a Nordstrom, B., Finkenzeller, U., Janko- location of the star in the Hertzsprung- quasi-period (of about 49 days) was vics, 1.: 1989, Astron. Astrophys. Suppl. Russell diagram, which is determined by found in the light variations of the star Ser. 78, I. the evolutionary state of the object? HR 5999 (A7 Ille) by Baade and Stahl Zajtseva, G.V.: 1986, Astroph. 25, 626. Many observations were also made simultaneously with spectroscopic ob- servations. For the study of the variable emission lines in the visual and/or in the UV, the knowledge of the brightness level of the star at the time when the spectroscopic observations were made, is necessary. Recent results of such studies have been reported by Tjin A Djie et al. (1989), for the visual spectral region, and by Blondel et al. (1989), for the ultraviolet.

Correlation Between Light and Colour Variability A specific problem shown by several Herbig Ae/Be stars is that the light varia- bility is correlated with the changes in colour in a special way. In the beginning, the colour of such a star becomes red- der when the star dims, but after reach- Ab- Ay ing a certain "turning point", it gets bluer Figure 3: The magnitude-colour relation of UX Or;. The star becomes redder when it dims, but when becoming fainter again. A typical after a certain turning point it gets bluer when decreasing in brightness further. The 1990 Outburst of VY Aqr M. DELLA VALLE and T. AUGUSTEIJN, ESO

Introduction The sixth outburst of VY Aqr in the last eight years was recorded by several amateur observers on June 30.75 U.T. 1990 (IAUC 5046). Thanks to the exten- sive monitoring, the observed maximum mv = 10.4, should be very close to the true one. The spectroscopic and photo- metric observations began at La Silla some nights later, with the ESO 1.5-m and the Dutch 90-cm. The visual light- curve, represented in Figure 2, has been derived by plotting the magnitudes pub- lished in the IAU Circulars (5046, 5053) and the Walraven photometry obtained at the Dutch telescope. Figure 2 shows reproduced on the same scale the light curves observed during the other five recent outbursts (see Table 1). Originally, VY Aqr was believed to be a fast nova (Payne-Gaposchkin, 1957). This was due to the large amplitude of the outburst recorded in 1907 (- 10 m,,), and to the fact that the sec- ond eruption in order of discovery was detected only in 1962 (Strohmeier, 1962). On the other hand, the lightcurve of this star does not fit in many respects that of a classical nova. In particular it does not satisfy the well established relationship between the magnitude at maximum and the rate of decline Figure 1: VYAqr, the bright star near the centre of the picture, during the recent outburst. The (Capaccioli et al., 1989) or between the image was taken with the Nn-EMMI through an R filter on July 9 by Della Valle and Oosterloo. amplitude of the outburst and the rate of decline (Warner, 1987). On the contrary, Aqr are not at all comparable to those of intervals of years would allow us to in- the amplitudes and the recurrence times a classical nova. clude this star among the class of the of its outbursts fit very well to the Ku- In principle, the occurrence of out- recurrent novae (see Kholopov et al., karkin-Parenago relation for Dwarf bursts of large amplitude (7- 10 mag) at 1985), but in recent years a number of Novae (DN) : A(mag) = 1.85 + 0.44 + 1.40 + 0.23 x log^, (days) (van Paradijs, 1985). However, the most marked differences from novae come from the analysis of the spectra. Both at max- imum and at minimum the spectra of VY

TABLE 1: Recorded VY Aqr Outbursts

Year Maximum Band

8.4 8.0 9.0 11.0 + AAA 10.5 A A 9.7 9.5 16 0 10 20 10.3 LA 10.3 10.7 10.4 phase 11 .I 10.4 Figure 2: Composite lightcurve of VY Aqr in the recent outbursts. The phase is expressed in days after the maximum. observations argue against this view. In particular: (a) the low excitation spec- trum which characterized W Aqr at minimum (Hendry, 1983), (b) the short recurrence time exhibited by the stars in the last years, and (c) the spectrum at maximum typical of a DN in outburst. Roughly speaking, DNe form a fairly homogeneous class of variables. Their lightcurve is characterized by relative long intervals of quiescence, generally from some weeks to some months, in- terrupted by sudden rises in the bright- ness (typically 2-6 mag) which last less than one or two days. The subsequent decline takes typically a few days to a week. Figure 3: 4-minute Boller and Chivens spectrum of VY Aqr during the 1990 outburst. The Most of the DNe exhibit a spectrum at spectrum is calibrated in wavelengths and corrected for flat field and sky subtraction. minimum of low excitation with strong Balmer lines in emission, superimposed on a faint, blue continuum. Weak emis- sion lines of Hel are also present where- as the forbidden lines, quite common in the spectra of the novae at this stage, are generally missing. As a DN in- creases in brightness, the continuum becomes stronger and in place of the emissions, shallow absorption lines ap- pear, frequently filled in with emission. This type of spectrum was exactly what was observed (Augusteijn and Della Valle, 1990) during the recent outburst. According to the current models, the absorptions probably arise from the in- ner, rapidly rotating portions of the disk surrounding the primary. The emission comes from the outer layers rotating in a 4774.800 484!l.201 49ii.601 4'380.001 5048.402 quasi-Keplerian way. Figure 4: The H/3 absorption with the central re-emission. Among the DNe, due to the large am- plitude and the relatively long recur- rence time, VY Aqr represents a quite peculiar case. Actually, similar photo- metric behaviours have been recog- nized only in a handful of objects, like: DX And, UZ Boo, WX Cet, RZ Leo, UV Per, WZ Sag, SW Uma, and perhaps V1195 Oph.

The Observations Our observations were made on July 4-6, 1990, at the ESO 1.5-m telescope, equipped with the Boller and Chivens spectrograph and the CCD (GEC #I4 chip). Initially, we collected 33 spectra of VY Aqr in the 405-504 nm region, with a dispersion of 59 A mm-'. The bright- ness of the object (m, = 10.5) allowed tlllllllllIlllli us to keep a quite high temporal resolu- 0 10 20 3 0 tion (168 s). In the following nights, spectra covering the whole optical Time range (375-680 nm) of VY Aqr and V Figure 5: Plot of the integrated flux (arbitrary unit) for 33 spectra of VYAqr versus time. One unit 3885 Sgr, and in the range 375-505 nm in the abscissa corresponds to 168 s. of IX Vel and RW Sex were also taken. Finally, a new set of 21 spectra of VY Aqr in the 405-504 nm region, with a dispersion of 59 A mm-' with a temporal at the telescope, we derived the spectra the Johnson's V band through the col- resolution of 300 s were obtained. From shown in Figures 3-6. The Walraven our equation: VJ = 6.886 - 2.5 Vw - a rough reduction performed with IHAP photometry in V has been reduced to 0.082 (V-B(w (Pel, 1985). Figure 6: The spectrum of VY Aqr at maximum, in comparison with the "normal stage" spectra of three UX UMa stars: V3885 Sgr, IX Vel, and RW Ser.

Results the DN explosions. In the disk-instability served during their "normal" stage. The model the quiescent state is charac- strict similarity with the spectrum of VY A quick glance at Figure 2 shows terized by an accretion rate from the Aqr points clearly to a classification of clearly that VY Aqr undergoes two dif- disk onto the white dwarf (WD), smaller the UX UMa stars as DNe continuously ferent types of outbursts. The 1983, than the mass transfer rate from the in outburst, rather than Nova-like, as 1986, 1988, and 1990 outbursts are dis- secondary to the disk. As a result of this, normally reported. tinguished from the ones in 1987 and when the density in the disk has This fact is consistent with Krautter et 1989, by the longer duration and the reached a critical value, the disk al.'s (1981) suggestion, that the UX UMa greater brightness (-0.5 mag). It is suddenly changes its low mass transfer star TT Ari was undergoing, before worth noting that a qualitatively similar rate onto the WD, to a high accretion 1980, a standstill stage similar to the behaviour is found in the lightcurves of a rate state, originating an outburst. Later, long period of activity exhibited by the Z sub-class of DNe; the SU Ursae Majoris due to a decline in the density of the Cam type DN. stars. They exhibit, apart from the nor- disk, the DN returns to the minimum. In mal outbursts, the so-called superout- the mass-transfer-instability model, the bursts. In the case of VY Aqr, quiescent state is characterized by the References differences between the two types of same values of accretion rate from the Augusteijn, T., Della Valle, M.: 1990, IAUC outbursts can also be seen from the secondary to the disk and from the disk No. 5048. spectroscopy. The spectrum recorded to the WD. In this view, the outbursts Capaccioli, M., Della Valle, M., D'Onofrio, M., on July 5 (Figure 3), shows shallow ab- should be caused by bursts of the Rosino, L.: 1989, p. 1622. sorption due to Balmer lines, Hel and mass-transfer rate from the secondary Hendry, E.M.: 1983, Inf. Bull. Var. Stars, possibly N l (599.9 and 600.8, mult. 16), to the WD. The two different types of No. 2381. superimposed on a fairly strong con- eruptions observed in VY Aqr would Khopolov et al.: 1985, The General Catalogue tinuum. The H lines appear variously perhaps suggest that the star can of Variable Stars. filled in with emission and in some cases undergo both these mechanisms. Krautter, J., Klare, G., Wolf, B., Wargau, W., Drechsel, H., Rahe, J., Vogt, N.: 1981, As- appear double-peaked. In particular, the Figure 5 has been obtained by plot- tron. Astrophys., 98, 27. emission profile of HB is split into sever- ting the integrated flux (between 405 Leibowitz, E.M., Laor, A,, Mazeh, T., Brosch, al components (Fig. 4). The absorption and 514.4 nm) derived for the 33 high N.: 1987, IAUC No. 4418. profiles for the H and He lines were temporal resolution spectra, versus Payne-Gaposchkin, C.: 1957, The Galactic measured and compared with the de- time. The variation in the flux detected Novae, p. 199. scription of the spectrum of VY Aqr from the star, is consistent with a period Pel, J.W.: 1985, Internal Report, Leiden Ob- obtained during the "normal" maxi- of 0.059 t 0.005 days. In agreement servatory. mum of 1987 (Leibowitz et al., 1987). In within the errors to the superhump Strohmeier, W.: 1962, Inf. Bull. Var. Stars, the 1990 outburst, the observed value period of 0.064 days reported by Warner No. 15. van Paradijs, J.: 1985, Astron. Astrophys., for the FWZl of HP corresponds to and Livio (1987). 144, 199. - 5000 km s-', a 40 % greater value Finally, in Figure 6, we compare the Warner, B.: 1987, Mon. Not. R. Astr. Soc., than that observed in 1987. spectrum at maximum (405-504 nm) of 227, 23. According to the current knowledge, VY Aqr to those of three UX UMa stars, Warner, B., Livio, M.: 1987, Astrophys. Journ. two mechanisms are believed to explain V3885 Sgr, IX Vel and RW Sex, ob- Lett., 322, L95. I.2-mm Continuum Observations of IRAS Galaxies: Implications for Gas Mass and Cold Dust Component

P. AND RE AN^ ', A. FRANCESCHIN~~ and J. ROLAND~ 'ESO; Osservatorio Astronomico di Padova, Italy; lnstitut dNstrophysique de Paris, France

Introduction studied objects. In particular, the fluctu- Beam-switching is achieved by wob- New fields of research have been ation level generated by unresolved ran- bling the secondary in azimuth ON-OFF opened at ESO with the SEST 15-m domly distributed sources, given by the the source and nodding the telescope, antenna (see The Messenger No. 57), second moment of the N(S) distribution, resulting in a three-beam technique and in particular we find promising the can significantly constrain the small- which, therefore, allows comparison be- coupling between this telescope and the and intermediate-scale anisotropies of tween the source signal and that from MPlfR bolometer because of the very the Cosmic Microwave Background two nearby empty sky regions. The high sensitivity of this instrument. This (CMB) (Franceschini et al., 1989) even at wobbling amplitude was set to be much system will allow the investigation of the - 1 mm, i. e. near the peak of the CMB. larger than the optical radius of the continuum emission at millimetric At present, very few observations are galaxy. wavelengths of galactic and extragalac- available of the millimetre continuum Each source has been observed tic objects. emission of galaxies and they are mainly n .200 s times with n depending on the We have started an observational pro- biased towards active galaxies (both expected 1.2-mm intensity. To approxi- gramme, to be carried out partly with AGNs and starburst galaxies), because mately evaluate the millimetric flux the the SEST telescope, to investigate the of their enhanced nuclear emission. The IRAS I00 ym flux has been extrapolated 1.2-mm continuum emission of a com- only mm measurements available on by assuming a thermal spectrum with plete sample of galaxies selected from spiral galaxies are those reported by spectral index between 1 and 2. the IRAS Point Source Catalogue (Smith Chini et al. (1986), but the claimed con- Atmospheric transmission has been et al., 1987). spicuous presence of a cold dust com- monitored by frequent skydips. Uranus, Among the important issues which ponent peaking around 200 ym has not Mars, Neptune and Jupiter have been can be addressed from this project, we been confirmed by other submillimetre used as primary calibrators by assuming find of particular interest: observations (Stark et al., 1988; Eales et weighted effective temperatures at this (a) the study of the electromagnetic al., 1989). wavelength of 93 f 1, 200 -t 6, 96 k 2 spectra of galaxies at long wavelengths: The first observations have been per- and 169 * 3, respectively (Orton et al., late-type galaxies represent the majority formed at the IRAM 30-m telescope. To 1986; Gear et al., 1985). The quasars of the extragalactic sources detected by allow comparison between the mm flux- 3 C286, 0839 + 187, 0953 + 255, the IRAS satellite. Most of their ob- es with the IRAS observations and to 1156 + 295,2201 + 31 5 have been used served emission is thermal and comes avoid large systematic errors introduced as secondary calibrators mainly to de- from dust in HI clouds heated by the by aperture corrections, the angular di- tect sky variations during the observa- general interstellar radiation field, cold mensions of the galaxies should not ex- tions. dust in molecular clouds and dust ceed the beam width. Therefore, we The overall accuracy on the detected heated by hot stars embedded in com- have chosen galaxies of the sample with fluxes depends strongly on the atmo- pact H II regions. optical size comparable with the IRAM spheric conditions, being between 10 However, to understand both galactic 30-m beam width (HPBW = 11"). and 30%. evolution and star-formation processes, The 1.2-mm continuum emission of 7 which are strictly connected with the objects of the sample and 5 other galax- available dust and gas present in the ies has been studied and issues on the Results interstellar medium, one needs to know presence of a cold component of the Of 12 observed sources (7 belonging the total amount of these components in interstellar medium and dust and gas to the sample and 5 are isolated objects) the galaxy disks. The true dust column masses of the disks are preliminarily 9 have been detected and for the other 3 density cannot be properly estimated addressed. upper limits were obtained. Figure 1 only by means of the FIR measure- shows 4 IR/mm spectra, the IR fluxes ments, like those of the IRAS satellite, Observations have been taken from the IRAS Point since they are not sensitive to dust Source Catalogue (Lonsdale et al., colder than 20 K and the bulk of dust The observational mode is briefly out- 1989) and have been slightly modified mass is expected to emit at submilli- lined since most of the performances of according to the colour and K-correc- metre and millimetre wavelengths. Con- the IRAM 30-m antenna are equal to tions (Smith et al., 1987; Lonsdale et al., tinuum flux densities in this spectral those of the SEST. 1989). range are good tracers of the total dust, The observations have been carried The millimetre values have been also gas and molecular mass and can repre- out with the 3He bolometer of the MPlfR corrected for the overall system re- sent an alternative way to estimate fed by the IRAM 30-m telescope at Pico sponse and K-corrections. The former these parameters. Veleta (Spain) on March 17-1 8 and May has been evaluated by computing the (b) galaxy counts at these wave- 17-19, 1990. integral: lengths: the source distribution, N (S), The position of the sources was found and its first and second moments: by pointing a nearby radio quasar with I = J S. N(S)dS and (~l)'=J S2. strong millimetric fluxes. Pointing accu- N (S) dS, provide relevant constraints on racy was most of the time better than 2" models of cosmological evolution of the and was checked every half hour. wavelengths the flux density, Fh, de- pends linearly on the dust mass and its temperature (Draine, 1989):

where ,,(?L) are the grain opacities due to component i; < TI> is the time-average temperature (at these wavelengths it is possible to approximate the tempera- ture distribution of the grains with a sin- gle temperature) and M, is the dust mass. Gas masses are then obtained by adopting the relationship between the dust optical depth s and the hydrogen column density N(H2 + HI) given by the models. We estimated the dust masses of the clouds by using two different models of interstellar dust (Draine and Lee, 1984; Mathis and Whiffen, 1989). These mod- els provide values for the grain opacities 1 2 3 1 2 3 at 1 mm using different composition and log@) (PI dimensions of dust grains. Draine and Figure 1: IR/mm spectra of 4 of the observed galaxies. The 12, 25, 60 and 100 pm data have Lee (1984) assume that dust grains con- been taken from the IRAS P.S.C. (see text for details). Two thermal curves B,(Td) - 30 + sist of a mixture of spherical silicates 40 K (a - 1 i 1.5) (dot-dashed lines) and at Td - 20 K (a - 2) (dotted lines) are shown for and graphites with size distribution: comparison. j (a)da a-3.5 da for a varying between 50 r\ and 0.1 pm. Mathis and Whiffen (1989) model grains as fluffy aggregates of submicron-size particles composed where v, and v2 are the lower and upper spectral index must be fixed and this of various astronomical minerals whose limits on the system spectral response; can be done only by adopting a dust spatial structure is fractional and chemi- I,,, I,,, (v, W) is the atmospheric emission, model. In this case we used the values cal composition inhomogeneous. assumed to follow a cosecant law: I = of 1 t 2 as predicted by the most Therefore, grains can attain greater di- I e-ro(w)cosecEl o , t,(w) is the measured accepted models (e. g. Draine and Lee, mensions (from 0.03 pm up to - 1 pm). zenith optical depth for a given value of 1984). By using eq. (1) we find for the 7 the water vapour content w, El is the sources of the sample the values listed in Table 1. For each source both the elevation of the source; E(V, El) is the Dust and Gas Masses antenna efficiency and Y(v) is the optics cold dust component (from 1.2-mm ob- transmission. The underlying assump- The thermal emission from dust at servations), the warm component (from tion is that the spectra in the millimetric these wavelengths is optically thin, 100 pm IRAS data) and the evaluated region can be approximated by F = therefore one samples the entire line of values for the gas masses are reported. F,($f, F,($f, where a is the spectral index of sight and determines the total dust col- The first row contains values deduced the source. umn density; at mm and submm from the Mathis and Whiffen's model, A further correction applied to the millimetric fluxes, due to the different size between the beam width and the TABLE 1: Estimated dust and gas masses (in optical diametre, has been applied by assuming that the IR disk obeys an ex- Galaxy Cold dust (mm) Warm dust (IR) M,,, M(HI) ponential law: I(r) = Ioexp(-rho), a(r) = 09534+2727 (1.9 i 0.3) 1o6 * (6.4 0.3) 1o5 rc 8.1 10' 3.7 lo8 aoexp(-rho) (Xu and de Zotti, 1989; * + t(4.6 i 0.7)10"(8.6 i 1.3)105 t410' Bicay and Helou, 1990) and that the IR 5.7 1 and mm emissions are spatially corre- 10460+2619 * (2.3 + 1.0)107 * (4.5 + 0.7)106 * loi0 o9 t (5.5 f 2.3) 1o7 t (6.0 f 0.9) 1o6 t 1.3 10" lated (see for instance Andreani et al., 1990). 12341+2442 *(4.4+1.0)10~ *(7.3+1.1)10~ rc210i0 5.4 1o9 2 In Figure 1 is also reported a fit with a t (1.1 f 0.3) 10' t (9.8 1.5)lo6 t 3.9 10'' - modified Planck spectrum h-U B,,(T,) 13126+2452 rc (8.3 f 2.1)107 a (5.4 f 0.8)106 rc 3.4 10'' with a ranging between - 1.0 and 1.5 t (2.0 i 0.5)108 t (7.3 f 1.1)106 t 10" and T, - 30 t 40 K (dot-dashed line). 13387+2331 rc (8.2 i 3.1)107 a (1.4 i 0.2)107 rc 4.2 10" - However, the solution is not unique be- t(2.0 f 0.8)108 t(1.9 i0.3)107 tloil cause very likely the 60 km point is 15373+2506 -uc (3.7 + 2.1)107 * (5.4 f 0.8)106 rc 1.8 10" - affected by emission of smaller dust t(8.9 + 5.1)107 t(7.2 + 1.1)106 t410" grain at a much larger equilibrium tem- 15566+2657 rc < 1.8 1o7 *(1.3?0.2)10~ rc<7.810~ 4.310~ perature. In fact, by excluding the 60 pm t < 4.3 lo7 t(1.8f0.3)10~ t<4.310~~ point the curve matching the data has a lower temperature, Td - 20 K and a - 2 u Values deduced from Mathis and Whiffen's model. t Values deduced from Draine and Lee's model. (dotted line). Note that, in order to infer a M (H I) are taken from the literature (see text). value for the dust temperature, the and the second row those inferred from between lo8 and 5 . 10'' Ma and the IRAM 30-m antenna and help during the Draine and Lee's computations. When ratio M (H2)/M(H I) is of the order of 1. If observations, Dr. E. Kreysa for helpful available, the M(H I) masses calculated this is the case also for the observed suggestions and all IRAM staff for tech- by using HI 21 cm data are listed in the sources of our sample, the gas mass nical support. P.A. thanks ESO for the fifth column (Bicay and Giovanelli, 1987; values inferred from our measurements hospitality during the CNR fellowship Mirabel and Sanders, 1988; Young et al. would agree with those determined from supporting this work. 1989). CO and HI data. It should be stressed that the ap- proach used here is not claimed to be, Discussion and Conclusion up to now, of greater accuracy than References The main advantages on the determi- other determinations of gas masses P. Andreani et al., 1990, Astroph. J. 348, 467. nations of the dust mass at these (e.g. using the integrated intensity of the M.D. Bicay and R. Giovanelli, 1987, Astron. wavelengths lie on a better evaluation of '"0 line) but it is important either be- J., 93, 1326. M. D. Bicay and G. Helou, 1990, to appear in < Ti > since at higher frequency the cause it implies a completely indepen- Astroph. J., October. uncertainties in the temperature dis- dent method based on a different set of R. Chini et al., 1986, Astron. Astroph., 166, tribution function may introduce order- assumptions. However, these observa- L8. of-magnitude errors in < BjbO>. tions can substantially improve our B. T. Draine, 1989, in The interstellar medium Note that the warm dust masses knowledge on dust opacities at long in galaxies, ed. H.A. Thronson and J.M. listed in Table 1 can be underestimated wavelengths and constrain models of Shull, Dordrecht: Kluwer, in press. also because the IRAS 100 ym mea- dust grains. This would turn into a better B.T. Draine and H. M. Lee, 1984, Astroph. J., surements do not fully sample the total determination of dust and gas masses. 285, 89. dust in the galaxy disk. Therefore, we find this approach more S.A. Eales et al., 1989, Astroph. J., 339, 859. A. Franceschini et al., 1989, Astroph. J., 334, However, the uncertainties in the promising with respect to that based on 35. grain opacities are larger at long CO line intensities since the uncertain- W. K. Gear et al., 1985, Astroph. J., 291, 51 1. wavelengths even if they do not depend ties related to this latter are largely con- C.J. Lonsdale et al., 1989, Cataloged Galax- on the details of the size distribution. nected to the physical conditions of the ies and Quasars observed in the IRAS sur- Gas and dust masses are estimated, medium and then more difficult to vey, version 2, Jet Propulsion Laboratory. then, within a factor of 5 (see Table 1). evaluate. J.S. Mathis and G. Whiffen, 1989, Astroph. The comparison with M (H I) suggests Further observations will be carried J., 341, 808. that very likely there is a substantial out at SEST in September and they will I.F. Mirabel and D.B. Sanders, 1988, As- 335, contribution to the total gas mass due to be helpful in gaining statistical insights troph. J., 104. G.S. Orton et al., 1986, Icarus, 67, 289. H2. But, to draw any firm conclusion on into these problems. B. J. Smith et al., 1987, Astroph. J., 318, 161. this point we need CO line measure- A. Stark et al., 1988, Astroph. J., 337, 650. ments of these galaxies, which up to Acknowledgements J.S. Young et al., 1989, Astroph. J. Suppl., now have not been carried out. 70, 699. Young et al. (1989) found that for a We would like to warmly thank Dr. H. C. Xu and G. De Zotti, 1989, Astron. Astroph., sample of IRAS spirals M(H2) ranges Steppe for his kind introduction at the 225, 12.

Variability as a Way to Find Quasars: a Complete Sample M. HA WKINS, Royal Observatory Edinburgh, United Kingdom P. VERON,Observatoire de Haute-Provence, France

Introduction containing a sizeable fraction of the Van den Bergh et al. (1973) first sug- To study the cosmological evolution quasar population, they each suffer the gested using this property as a method of quasars, it is first necessary to estab- drawback that their detection efficiency for finding quasars, and Sanitt (1975) lish a complete sample. This has proved is strongly dependent upon redshift. To discussed the various types of variable to be particularly difficult, for several some extent they may be seen as com- star (RR Lyrae and low-luminosity M- reasons. Early work was based on radio plementary procedures as the UVX type flare stars) which might contami- surveys, and although this resulted in method is most efficient in the low red- nate a sample compiled by this method. well defined samples with no obvious shift regime, while slitless spectroscopy There are number of advantages in us- bias in redshift, it was inevitably limited is more sensitive to high redshift ob- ing variability as a search criterion for to a small subset of quasars (1 or 2 %) jects. However, what is clearly needed is quasars. There are essentially no instru- which themselves showed a wide varie- a selection technique which is essential- mental redshift biases, and apart from ty of radio properties. Most recent re- ly independent of redshift, and is ca- some constraints set by the passband sults are based on samples obtained by pable of detecting a substantial fraction of the search, there are no colour- or two main methods: the UV excess of all quasars brighter than a given flux magnitude-dependent biases. Set method (see Veron, 1983, for a review), limit. against this, there is the practical limita- later generalized to the multicolour Most, if not all, quasars are optically tion that the timescale of variation for method (Koo et al., 1986), and the slit- variable. Indeed, previous studies have most quasars is several years and so a less spectroscopy method (see Veron, shown that up to 70% of all quasars search must be undertaken over a de- 1983, for a review). Although both tech- have an amplitude of variability larger cade or more to detect a reasonably niques can produce samples apparently than 0.43 mag. (Trevese et al., 1989). high fraction of the quasar population. -100 0 100 200 300 0 LOO 200 300 400 B-R B-R Figure 1: U-B/B-R diagram (U-B and 5-R are in units of 0.01 mag.) for: (a) all variable quasar candidates with dB 2 0.45 mag.; (b) all variable quasar candidates with 0.30 5 B 5 0.35; (c) variable candidates with dB 2 0.35, the objects near a bright star and the extended objects being excluded (809); (d) the extended objects (690).

Preliminary attempts to discover MOS measures of UK Schmidt plates nitudes for each image, as well as ex- quasars on a large scale solely on the aimed at detecting almost all quasars in tensive additional measures in UVRI. basis of variability were undertaken by a 19 sqare degree field. Our results to The actual search for quasars was Hawkins (1981, 1983, 1986) using COS- date are described in the following sec- constructed to detect objects which MOS measures of a number of Illa-J tions. varied significantly from year to year, but plates taken with the UK 1.2-m Schmidt which remained essentially constant telescope. This early work established within each of the eight measurement The Survey for Variable Quasars that variability was indeed a viable way epochs. This had the effect of removing to find quasars, but dit not cover a long The survey for variable quasars has essentially all types of variables apart enough time span to detect more than a been based on the ESOISERC field 287 from quasars, as well as most non-vary- small percentage of quasars in the field. at 21 h25m,-45'. The first plates of this ing objects with large photometric This is because, in most cases, the field were taken in 1975, and since then errors. It also tended to remove quasars standard deviation of the variability is the field has been extensively photo- with large variation over short time significantly smaller in the case of a graphed in UBVRI. In order to detect scales (OW quasars), but these objects short epoch survey (2 yr) than for a long variables, several Illa-J plates (33 al- are known to be very rare. The selection epoch (50 yr) (Angione et al., 1981), al- together) were obtained in each of the algorithm divided the maximum am- though the mean brightness remains years 1977, 1978 and 1983-88. The plitude of variation by the aggregate essentially constant over 60 to 70 years plates were all sky limited (approx. 60 r.m.s. scatter within each epoch, to give (Angione, 1973). min exposure) and reached a limiting a measure o of the significance of the The influence of the time dilation due magnitude of about Bj = 22.5. variability. to redshift on surveys of variability de- The photographs were measured us- We have first selected all (2450) ob- pends on the nature of the variability ing the COSMOS machine at ROE and jects with a variability amplitude larger (Gaskell, 1981); however, if the r.m.s. calibrated with deep CCD sequences than AB = 0.30 and brighter at minimum variation increases with time to reach its obtained at La Silla and with the AAT than B = 21.5; however, we have found maximum after two years for quasars at (Hawkins, 1983). This measurement that the contamination by non variable z - 1, as found by Bonoli et al. (1979), it procedure provides some 20 parame- objects is very large (-90%) for AB < is clear that the same value will be ters per image, including position, inte- 0.35; we therefore restricted our sample reached only after four years at z - 3. grated magnitude and some image to AB 2 0.35 (1241 objects). Moreover, Over the last 12 years we have been structure information. The measures of we have excluded a small area around undertaking a survey based on COS- each plate have produced 33 B mag- the 300 brightest stars in the field, total- have extracted all objects in the field with U-B 5 -0.40, y < 0, and B,,, 2 21 .O, irrespective of their variability. We have found 602 such objects. 325 of them have an amplitude of variability AB 2 0.35. This suggests a complete- ness level of 54 %. However, 45 objects have B-R < 0, only two of them with AB 2 0.35; they are most probably hot stars; this brings the statistic to 323 variable quasar candidates for a total of 557, or 58 %. Comparison of the histograms of the U-B colour index for the highly variable Figure 3: Fractions of the variable quasar candidates (galaxies and objects near a Figure 2: Histograms of 'Y'' for the objects objects (AB > 0.50) and the low varia- bright star excluded) with y < 0 in various with dB 2 0.45 mag. and for the objects with bility objects (AB < 0.30 and B-R > 0) bins of variability amplitude. 0.30 5 dB 5 0.35. suggests that only half of those are quasars; the other half could possibly be the weak blue galaxies found by ling 3665 mm2 or 1.28 deg2, because Gallagher and Hamilton (1988) and Koo where contamination from non-vari- measurements of weak stars near bright (1986). If this is the case, 90 of the low ables is not significant, is about 70% stars are very uncertain. Galaxies were variability objects would not be quasars complete. So far, most work has been removed from this sample using an al- and therefore the variable quasars (323) done from searches based on blue gorithm based on maximum density ver- would constitue 69% of the total. passband plates, but we now have a sus image area, using twelve of the baseline of 9 years for red passband plates, which should provide an excel- plates with the best seeing. The result- Spectroscopy ing sample contained 809 quasar can- lent basis for searching for quasars in didates. In the course of several observing the redshift range 3.5 to 5. runs with the AAT and the ESO 3.6-m telescope, we have made spectroscopic References Reliability and Completeness observations of 176 variable objects. Angione, R. J., 1973, Astron. J. 78, 353. We have to ask how many of these 140 of them turned out to be quasars, Angione, R.J., Moore, E.P., Roosen, R.G. objects are quasars and how many 48 having z > 2.2, the largest redshift and Sievers, J., 1981, Astron. J. 86, 653. quasars have been missed. being z = 3.58 (# 695); there is a bias Bonoli, F., Braccesi, A., Federici, L., Zitelli, V. In a first step, we compare the U-BI against redshifts larger than this value in and Formiggini, L., 1979, Astron. Astro- 35, B-R diagrams for the highly variable ob- a survey based on Illa-J plates because phys. Suppl. 391. Gallagher, J.S. and Hamilton, D., 1988, As- 2 for larger redshifts, a large k correction jects (AB 0.45 mag) and for the low trophys. J., 330, 661. variability objects (0.30 2 AB 5 0.35) applies due to Lya leaving the band- Gaskell, C. M., 1981, Astrophys. Letters 21, (Fig. 1); we immediately see that, if we pass. Three additional objects are Sey- 103. call y = (U-B) + 0.74 (B-R) - 0.32, almost fert 1 galaxies (# 23, 21 1 and 746); two Hawkins, M. R.S., 1981, Nature 293, 116. all highly variable candidates have y < 0 more (# 7 and 24) show a continuous Hawkins, M.R.S., 1983, Monthly Not. Roy. while very few low variability objects spectrum and have a strong polarization Astr. Soc. 202, 571. have. Figure 2 shows the histograms of as shown by measurements made at La Hawkins, M.R.S., 1986, Monthly Not. Roy. y for the two classes of objects. It clearly Silla with a Wollaston prism; they are Astr. Soc. 219, 417. Koo, D.C., 1986, Astrophys. J. 311, 651. shows that most quasars have y i 0 most probably BL Lac objects. Two ob- Koo, D.C., Kron, R.G. and Cudworth, K.M., and that very few low variability objects jects (# 19 and 668) are dwarf novae; 1986, Publ. Astr. Soc. Pacific 98,285. are quasars. the others are galaxies (3), stars or ob- Sanitt, N., 1975, Nature 258, 586. From the total of 809 variable can- jects of unknown nature due to a poor Trevese, D., Pittella, G., Kron, R.G., Koo, didates, 587 have y i 0. Figure 3 shows signal-to-noise spectrum. Of those ob- D.C. and Bershady, M., 1989, Astron. J. the fraction of candidates with y 5 0 in jects, all have a positive y except for the 98, 108. various ranges of variability amplitude. two dwarf novae and two objects of Van den Bergh, S., Herbst, E. and Pritchet, For AB 2 0.50, this fraction is constant unknown nature (# 10 and 24); this con- C., 1973, Astron. J. 78, 375. and equal to -90%; it rapidly drops for firms that most objects with a negative y Veron, P., 1983, 24th Liege International As- lower values of AB, being only 42 % for are quasars. trophysical Colloquium, p. 210. 0.35 5 AB < 0.40. Among the 39 ob- jects with AB 2 0.50 and y > 0, 18 are Conclusions confirmed Seyfert 1 galaxies or quasars (and 9 have z > 2.7), 7 are either stars or This paper is a first step to addressing STAFF MOVEMENTS galaxies while we have no spectra for 15 the problem of obtaining unbiassed of them. samples of quasars, especially with re- Departures On the other hand, all 73 objects with gard to redshift, for the purpose of Europe: AB 2 0.50 and y 5 0 for which we have studying the evolution of the luminosity MAASWINKEL, Alphonsus (NL), a spectrum are confirmed quasars ex- function. We have reasons to believe Project Engineer in Astronomical cept one which is a dwarf nova, there- that the strong redshift biases associ- Instrumentation fore at least 94% of all highly variable ated with other methods of finding PRIEUR, Jean-Louis (F), Fellow objects are quasars. quasars are not relevant to selection by ZHAO, Gang (RC), Associate To find out how many quasars we variability. With a well sampled search have missed because they have a varia- period of some 11 years, we have Chile: bility amplitude smaller than 0.35, we shown that our sample, in a regime LE BERTRE, Thibaut (F), Scientist A Search for Interstellar Be II h 3130: CASPEC Shakes Hands With IUE and GHRS D. BAADE and P. CRANE, ESO

The wavelength region near the from observations from the ground 31 30 A. Therefore, our only chance was atmospheric high-frequency cut-off is (Boesgaard, op. cit.). to submit an application for observing still a considerable challenge for high- time with CASPEC. We were allocated resolution spectroscopy. The sensitivity Observations two nights in May 1990. of both IUE and GHRS on HST drops We used CASPEC with the 31.6 lines/ steeply at wavelengths where atmo- For the detection of isolated spectral mm echelle grating (which has twice the spheric absorption still is a substantial features, a spectral resolution, Ah, efficiency of the 51.6 lines/mm grating in handicap for ground-based observers. roughly equal to the line width is close to the UV), the Long Camera (which pro- The situation is even worse if signal-to- optimum. This would have made the vides a better sampling, i.e. reduces the noise ratios considerably in excess of CES the instrument of choice. However, effect of small-scale detector blemishes 100 are also required and which are not towards the UV, the high-efficiency and facilitates the definition of order and within easy reach of either IUE or GHRS. multi-layer coatings of the optical sur- inter-order space), and a coated (for faces of the CES have an extremely higher UV response) GEC CCD (ESO Scientific Background steep fall off in throughput which sets in No. 7) which has 576 x 385 pixels of at wavelengths noticeably longer than 22 x 22 ym. With this configuration, we One of the most interesting spectral features in this domain is the strongest line of Bell at 3130.4 A (in most of the relevant astrophysical environments, the singly ionized atom will by far be the First Announcement of the 3rdESOIST-ECF dominant ionic species). With atomic number 4, this element is just at the limit Data Analysis Workshop where some non-standard big-bang ESO, Karl-Schwarzschild-StraBe 2 model calculations predict traces of D-8046 Garching, FRG primordial abundances (e.g., Boyd, R. N., Kajino, T.: 1989, Ap. J. (Letters) April 22-24, 1991 336, L55). The main source of beryllium The aim of the Workshop is to provide a forum for discussions of astronomical is probably the spallation by cosmic software techniques and algorithms. It is held annually during the spring (ApriVMay) and rays of heavier nuclei in the interstellar centres on a different astronomical area each time. Due to available space, participa- medium. Knowledge of the efficiency of tion will be limited to 80 people. At the last Workshop several people could not be accommodated and we therefore recommend that you send in the corresponding the spallation process and the con- participation and accommodation forms well before the deadline. comitant depletion onto dust grains is The topic for the 1991 Data Analysis Workshop will be analysis of direct imaging very essential for assessing the primor- data. The scientific section of the meeting will consist of three sessions each starting dial abundance of lithium, the element with a main talk followed by presentation of papers of 5-10 minutes duration. The last which is the most important cosmologi- day is reserved for general user meetings for MlDAS and ST-ECF. cal diagnostic. In stars, beryllium is The tentative agenda is: quickly destroyed at temperatures Analysis of Direct Imaging Data above about 3.5 x lo6 K. It can, there- April 22: 14.00-18.00: Digital Filters fore, be expected to be seen only in cool April 23: 09.00-12.30: lmage Restoration stars where, so far, crowding in the 14.00-1 7.00: Decomposition techniques 313-mm region has permitted only up- 17.00-1 8.00: European FITS Committee per limits to be determined (e.g., Ryan, April 24: 09.00-12.00: MIDAS users' meeting S.G., Bessel, M.S., Sutherland, R.S., 12.00-13.00: European FITS Committee Norris, J.E.: 1990, Astrophys. J. (Let- 14.00-1 7.30: ST-ECF users' meeting ters) 348, L57; Rebolo, R., Molaro, P., Contributions on algorithms and techniques, e.g. removal of cosmic ray events on Abia, C., Beckman, J.E.: 1988, Astron. CCD's, digital transformations, deconvolution, decomposition of images and fitting Astrophys. 193, 193). techniques are especially welcome. We encourage people to present their work in Also in the interstellar medium, only these areas even if it is only ideas. After each introductory talk, we will have a more upper limits have so far been obtained informal discussion where such contributions can be made. We also plan to have a (Boesgaard, A.M.: 1985, P.A.S.P. 97, poster session where people can present short contributions. Proceedings of the scientific sessions will be published. 37). They suggest that from space the The scientific organizing committee includes: P. Grosbd (Chairman) P. Benvenuti best strategy would presently be to go L. B. Lucy S. D'Odorico to fainter sources with large column D. Baade R.H. Warmels densities which can be detected even at Contact address: Secretary of relatively low S/N. By contrast, there lmage Processing Group, seems to be a niche for ground-based European Southern Observatory, efforts if a large light-collecting area is Karl-Schwarzschild-StraOe 2, combined with a low-noise detector. D-8046 Garching, FRG. The best upper limits on the equivalent EARN: DAWQDGAES051 width of interstellar beryllium lines SPAN: ES0::DAW (down to 0.23 mA) have, in fact, resulted 3 130 3135 3140 3145 3150 Wavelength [A] Figure 1: Normalized spectrum (sum of four exposures for a total of 165 minutes; step size 0.05 A) of < Oph in order 181 of the 31.6 lines/mm echelle grating of CASPEC. Absorption lines of interstellar CH at 3137.5, 3143.2, and 3146.0A are marked. The arrow points to the expected position of the Bell h 3130 line that had been searched for. The spikes at 3140 are caused by a detector blemish. Broad absorption features should be of stellar origin; the strongest one is due to 011 h 31 34.8. could observe orders Nos. 164-1 88, now available also at La Silla.) With the appears to us from this experiment that i.e. apprpximately the range from 3000 help of Alain Gilliotte and Philippe Car- flatfield or trailed stellar exposures with to 3500 A, and there was a small overlap ton, both problems were efficiently the slit length chosen such that neigh- in wavelength between neighbouring solved. bouring orders just touch one another orders. For the flatfielding we tried an entirely (and taken at the correct grating angle) We basically faced two technical new approach because at the short could provide a useful basis for model- problems. The first was (as was known wavelengths fringing in the CCD should ling the echelle blaze function. in advance) that the light from the inter- not be a problem. Therefore we turned nal calibration lamps (flatfield and com- the echelle grating to a pcsition corre- Results parison spectrum) normally goes sponding to about 4000 A where the through a non-quartz prism which, of transmission of the prism is still good. Unfortunately, we cannot report any course, at our wavelength had to be by- We then took a flatfield exposure with new scientific results. Shortly after we passed. The installation of a quartz the slit expanded close to its maximum had geared up the instrument on the prism is now being considered, but has physical length. This had the effect that first night, clouds moved in which were not yet finally been decided, so that anywhere on the CCD a large number even worse on our second night and observations at these short wavelengths (-20) of echelle orders were superim- thus reminded us strongly of additional cannot presently be offered to Visiting posed on one another so that the CCD reasons why there are space obser- Astronomers. The other problem was was relatively uniformly illuminated. As vatories. Therefore we had to concen- the identification of "our" order (No. 181) far as we can tell from our preliminary trate our observations mainly on the which was so far beyond the range analysis, this method is quite useful for bright (m, = 2.6 mag) 0-star Oph. Be- mapped in ESO's standard atlas of the correction of detector blemishes cause of the very steep decline of the the thorium spectrum (S. D'Odorico, M. such as column-to-column offsets overall throughput, orders 165-1 77 Ghigo, D. Ponz: 1987, ESO Scient, Re- which cannot be removed with standard were at least partly saturated while port No. 6) that we had to approach it flatfield exposures. Obviously, it should orders above No. 184 (3075A) were via two intermediate settings. (Mean- be generally valid for echelle observa- severely underexposed. In Figure 1, we while, we have prepared a simple exten- tions, irrespective of the instrument or show for order No. 181 the sum of four sion of the atlas for the 31.6 lineslmm the wavelength range. spectra with a total exposure time of echelle grating towards 3000 A which is Although we have not tried it, it 165 minutes (the last third of which was noticeably compromised by clouds). 4.0 mA, respectively, are easily seen. ing feasibility study (which also included The signal-to-noise ratio per spectral But there is no feature in excess of 1 mA the reduction of our data with the resolution element (0.1 A or -3 pixels), at 3130.4 A. This value corresponds to echelle package in MIDAS). Neverthe- was slightly better than 300. For the the strongest feature within 0.2 A of the less, we believe that it is perhaps worth centre of this order we estimate an over- expected position of Bell whereas the reporting it to the readers of the all efficiency (incl. atmospheric extinc- signal-to-noise ratio suggests a formal Messenger, and we certainly feel en- tion) of roughly 0.03%, down by nearly upper limit of 0.3 mA. Impressive couraged to make another attempt. two orders of magnitude from the effi- though these numbers may be, they are We thank Fons Maaswinkel and Ber- ciency measured with CCD No. 8 at only about the same as the ones in- nard Delabre for their expert advice on 4000 A (Pasquini, L., D'Odorico, S.: ferred by York and Snow (1982, Astro- the choice of instruments and instru- 1989, CASPEC, ESO Oper. Man. No. 2). phys. J. 255, 524) from their observa- ment modes and Alain Gilliotte and In Figure 1, the interstellar CH lines at tions with the Copernicus satellite. Philippe Carton for their competent and 3137.5, 3143.2, and 3146.0 A with equi- In the final analysis, our experiment tireless efforts to get CASPEC properly valent widths of about 3.7, 7.0, and was only a successful and very promis- set up.

EMMI, the ESO Multi-Mode Instrument, Successfully Installed at the NTT S. D'ODORICO, ESO

The EMMl Project sented at the 16th meeting of the ESO Hans Dekker; Bernard Delabre was re- Scientific Technical Committee. The ini- sponsible for the optical design and In November 1985, a conceptual pro- tial concept had been put forward the Heinz Kotzlowski for the mechanical posal for a spectrograph for the 3.5-m year before by J.L. Tanne and the au- layout. New Technology Telescope was pre- thor and later modified and improved by The execution of the project started at

Figure 1 : EMMl mounted at the Nasmyth focus B of the NT. The light-blue painted fork of the telescope is visible in the aperture of the air- conditioned instrument room. The adaptor/rotator is hidden by EMMl and its electronics. The colours of the panels of the cover identify the blue and red channels and show the optical path of the light in the instrument. The service platform in the forefront is also used to support the instrument when it is dismounted from the adaptor. BLUE ARM

Figure 2: EMMI is shown without the protective cover in this photograph taken at the end of the integration period in Garching. The sketch below identifies the main functions: (1) mode selection mirrors, (2) adjustable slit, (3) beam-splitter wheel, (4) below slit filter wheels, (5) collimators, (6) grating units, (7) folding mirrors, (8) field lens, (9) grism and filter wheels, (10) cameras, (1 1 and 12) detector heads and cryostat, (13) control electronics, mounted eventually in a slightly different way in the real thing, (14) detectors electronics, not installed at the time of the photograph.

the beginning of 1986. Both the optical mainly from European industries, usual- installed and successfully tested at the and the mechanical detailed designs ly with the standard ESO tendering pro- telescope (Fig. 1). While written three were entirely conceived at ESO; the cedure. A review of the main industrial weeks only after the first observations, same is true for the electronic hardware subcontractors for EMMl is given in the this paper gives a brief overview of the (including the control cameras for the insert on page 54. project and wants to make prospective two detectors) and the software. The About 5 years after its conception users aware of its capabilities. A de- mechanical parts, the optical and the EMMl (the ESO Multi-Mode Spectro- scription of the optical design and of the electronic components were procured graph as it came to be named) has been original performance goals can be found 52 EMMl is the first optical instrument for astronomical observations which offers wide field imaging, long slit, low and medium resolution spectroscopy and echelle spectroscopy on line, with the possibility to switch from one mode to the other in a matter of seconds. Only the Hubble Space Telescope, with its 5 focal plane instruments, offers a similar broad choice of observational capa- bilities: the two differ so much in terms of the scientific goals that a com- parison, however tantalizing, is not pos- sible. The complexity of the dioptric optical design of EMMl does not penalize the efficiency: in all modes this is as high or better than similar instrumentation at the other ESO telescopes (see the curves of the optical transmission of the optics in the March 1990 issue of the Messengerj. With its wide choice of observing Figure 3: The "EMMl's corner" of the control room. From the left, in the lower row, a Ramtex modes, EMMl makes possible to select dedicated to the user's interface displaying the layout of EMMl and the functions on line (a the Observing programme according mouse is used to select other display options), a terminal for the exposure definition and a the conditions of the atmosphere, in Ramtex displaying a long slit spectrum. In the row above two monitors for guiding and a particular the seeing and the sky bright- graphic display. ness, and to complete within a night a

in Proc. SPlE 627, p. 339 (1986). More information will be available in the Operating Manual (a first draft will be prepared by November 1990) and in de- dicated technical reports, to be issued in 1991. As stated in the minutes of the 1985 STC meeting "key factors in the defini- tion of the instrument were the expected excellent image quality at the NlT, the need to complement and when possible to improve 3.6-m instrumentation and the desire to minimize change-overs and maintenance". The concept which was finally adopted is that of a dual beam instrument, fully dioptric and based on the white pupil principle. The main advantages of this type of design are a very high efficiency in both channels, easy conversion from the grating to the imaging and grism spec- troscopy modes, and relatively cheap optics due to their small size. The instru- ment can be easily adapted to a new detector by building a proper camera: we took advantage of this option when the CCD originally foreseen, a 2048~pixel chip, was not delivered as planned. The depth of the 1.5-ton in- strument is 28 cm only to keep the momentum on the adaptor small and increase the stiffness. The symmetrical supporting structure gives easy access to all the parts of the instrument even Figure 4: A 300 s exposure of NGC 5128 in the Z colour exemplifies the size of the EMMl field with the present Th 1024 pixel detector (7.5 x 7.5 arcmin in red channel). The FWHM of the when this is mounted at the telescope. stellar images in this exposure is 0.85 arcsec. The present pixel size in the red channel (0.44 The various moving functions, most of arcsec) is not well suited to exploit the intervals of best seeing at the NTT. ESO plans to them of new design, are built in a way to introduce a CCD with a pixel size of 15 microns, corresponding to 0.35 arcsec, and it is optimize reliability and minimize mainte- building a CCD camera for direct imaging, to use in parallel with EMMI, with a pixel size of nance (Fig. 2). about 0.1 arcsec. the current operating modes of EMMl MAIN INDUSTRIAL SUBCONTRACTORS and a list of the filters, gratings and grisms which are currently available. The modes successfully tested in July OPTICS: Galileo (Italy) and Fisba (Switzerland) are: COATINGS: Matra (France) direct imaging in the red channel FILTERS: Andover (USA) and Soptel (France) (spectral range 400-1 100 nm, field GRISMS and GRATINGS: Milton Roy (USA) 7.5 x 7.5 arcmin, pixel size 0.44 arc- DETAIL DESIGN: Techno (FRG) sec) with the choice of 8 filters in a STIFFNESS ANALYSIS: BCV Progetti (Italy) single run. MECHANICAL STRUCTURE: De Pretto-Escher Wyss (Italy) grism spectroscopy in the red MECHANICAL FUNCTIONS: Enraf-Nonius (the Netherlands), Technica (Swit- channel with a 7.5 arcmin slit or slit- zerland), Geissler (FRG), Kern (FRG) less up to Rs (resolving power by slit COVER: Brunet Sicap (France) width in arcsec) about 1000 and with SERVICE PLATFORM: Genius-Klinkenberg (the Netherlands) a choice of 8 grisms. OPTICAL ENCODERS: Heidenhain (FRG) and Litton (USA) 6-arcmin slit grating spectroscopy in the red channel with Rs between MOTORS: Portescap (Switzerland),Faulhaber (FRG), In- land (USA) 1300 and 5500. Two gratings can be mounted at any given time. LIMIT SWITCHES: Baumer (Switzerland) echelle spectroscopy in the red CCD MOUNTINGS: NTG (FRG) channel at Rs = 7700. CCDs: Thomson (France) direct imaging in the blue channel (spectral range 300-500 nm, field 4.9 x 4.9 arcmin, pixel size 0.29 arc- sec) with the choice of 8 filters in a single run. programme which requires data of dif- way efficiently through the various 4.5-arcmin grating spectroscopy in ferent formats. observing options. If this will prove to the blue channel with Rs between The first months of operation of EMMl be the case, the introduction of some 400 and 11000. Grating housing as in will be used to gather experience on the form of service observing, with its the red. best way to operate it at the telescope. pros and cons, will have to be properly Two THX Thomson CCDs (1024~, Some procedure of flexible scheduling debated. 19 pm square pixels) are presently used will have to be introduced to exploit the as detectors in the two channels. The CCDs have been coated at ESO with periods of best seeing at the NTT for the Present Capability and Future programmes which require it at most. special dyes to enhance the UV-blue Prospects Another concern is represented by response. The quantum efficiency curve the difficulty a visiting astronomer (who The Application Form for Observing has a peak of about 50 % at 600 nm and sees the instrument 5-6 nights a year Time at La Silla in Period 47, distributed levels down to about 19% in the UV- only) may encounter in making hislher in August 1990 includes a description of blue region. The read-out noise mea-

Figure 5a, b: These two scientific exposures, a large field direct image and an echelle spectrum, have been obtained with EMMl at a time separation of a few minutes. lmage (a) is a 600 s direct exposure of the supernova remnant RCW 89 taken in the red arm through an interferential filter centered on Ha. lmage (b) is an echelle spectrum of a bright filament selected from the previous exposure. The spectral range covered by the 10 orders shown in the spectrum is 610-980 nm, the resolution 45 km/s, the length of the slit 20 arcsec. The emission lines from the remnant can be distinguished from the sky lines for their non-uniform, structured appearance, caused by density and velocity fluctuations. Visible in the three orders at the bottom are the [Ol] 630 nm, [NIl] 654.8, 658.4 nm, Ha and [Sll] 671.7, 673.1 nm emission lines; in the two orders at the top the [Slll] 906.9, 953.2 lines. sured at the telescope is 4-6 electrons, the dark current is less than 3 e-/pixel/ THE EMMl PROJECT TEAM hour at 140 OK. The global efficiency curves for all P. Biereichel: CCD Software observing modes have been computed B. Buzzoni: Testing of the optical components from the transmission curves of the op- S. Deiries: CCD and dewars integration and testing, CCD coating tics, filters, grisms and grating and from the efficiencies of the CCDs, all mea- B. Delabre: Optical design sured in the ESO laboratories. They are H. Dekker: Optical concept, procurement of the optical elements, testing of available in graphic and digital forms. the instrument off and on the telescope (Project Coordinator) Most important, they have been con- Astronomical specifications and project supervision (Project Re- firmed by the observations. As data are sponsible) being reduced, it appears that the com- G. Hess: CAD design and drafting. Preparation of the Call for Tenders for bination of highly efficient optics, low mechanical parts. Documentation read-out CCDs and sub-arcsec images G. Huster: Design of the CCD mounting head at the NlT will bring the performance of H. Kotzlowski: Mechanical concept and design of the overall instrument and its the instrument above the original expec- functions. Supervision of realization. (Coordinator of mechanics) tations. J. L. Lizon: Integration, testing and optimization of the instrument functions Many technical aspects of EMMl de- and of the overall instrument in the Garching laboratory and at serve to be described in detail and this the observatory. will be properly done in the future tech- A. Longinotti: CCD VME software, EMMl software nical reports. There are two points worth W. Nees: Design, procurement and testing of the control electronics mentioning here. There is a need in T. Oosterloo: Commissioning at the telescope and analysis of the results EMMl to minimize the flexures because G. Raffi: Overall EMMl software of the large rotation rates which occur R. Reiss: CCD control system and detector optimization close to the zenith in an Alt-Az tele- J. Roche: Ramtex user interface scope. Even if these can be avoided by properly planning the time of the obser- vations, the tests at the telescope have shown that the flexures in the most criti- cal modes (the red and blue medium ject spectroscopy using "punched" slits larger than originally foreseen and does dispersion) are well below 10 ym, the in an aperture plate. not permit to exploit the optical quality performance goal, for rotations up to It is important to note that the pixel of the telescope when the atmospheric 100 (red channel) and 180 degrees (blue size in the red channel of EMMl (0.44 seeing is very good. We had originally channel). Further optimization work is arcseclpixel with the Thomson CCD) is planned and built a slower camera to be going on at some of the critical units to further improve these values. Another source of initial concern, the grating units, have proved to be reliable and accurate "in the field". One housing mounts two gratings back to back which can be remotely selected and po- sitioned. The positioning can be repro- duced and it is stable to better than 111 0 of a pixel, an achievement which has been made possible by a control unit of new design. The final EMMl control programme, which integrates the operation of tele- scope, adaptor, instrument and of the two detectors, was being tested in July and was not used during most of the observations. The hardware set-up dis- play is however already in place. The "EMMI" corner in the control room of the Nl7 is shown in Figure 3. EMMl will undergo another commis- sioning period in October before being Figure 6: A portion of a 2-hour CCD exposure on the quasar 0000-26 (m, = 17.5, z = 4.1) taken offered to the first regular users. At that with EMMl in the echelle mode. A 60 grooves/mm echelle with blaze angle 28.7 degrees was time, besides installing the user inter- used with a 360 grooves/mm grism as cross disperser. The resolving power with the 1-arcsec face of the software, we will test three slit used for this observation is 39 km/s. The spectral range covered in one frame is operation modes which are foreseen to 420-800 nm, this figure shows the range 520-750 nm only. The length of the slit as shown by become fully operative in period 47 the height of the sky lines is 20 arcsec. In this observing configuration the global efficiency of the observation (product of the transmission of the atmosphere, telescope, instrument optics (starting April 91). These are the dichroic and detector) has a peak value of 7%. This high value combined with the small slit losses beam-splitter for spectroscopy in the (courtesy of the average good seeing at the Nmand the low read-out noise of the CCD (4 e-/ two channels at the same time, echelle pixel) permits to reach good S/N in the spectra of objects as faint as mag. 18- 19 in a few hours spectroscopy with a 31.6 grooveslmm integration. In this example, the Lyman a emission of the quasar is visible in the central orders, echelle giving a resolving power of a portion of the Lyman a forest in the lower ones. The S/N in the extracted orders varies in the 28,000 in the red channel and multiob- range 20-30. used with a 2048' CCD from Tektronix, vations. Many of them were obtained Acknowledgements which has not yet materialized on the with a specific goal in mind (e.g. stability market. A faster camera was then built tests during long integration, measure- The successful maiden voyage of to match smaller CCDs without too se- ments of the absolute efficiencies in the EMMl is the result of the efforts of sever- vere losses of the spectroscopic various observing modes, testing of the al persons at ESO. Some contributed to capabilities, but paying a price in terms photometric accuracy and of the image a very specific task only, others have of sampling frequency of the images in quality, testing of polarization effects spent a large fraction of their working the detector plane. Two actions are by mirror 3, etc.). The analysis of the time in the last four years on the project. underway to improve the situation by data will further verify these aspects of The table at page 55 is an attempt to the beginning of 1991: ESO will install a the performance of the instrument at identify the EMMl project team and their CCD of smaller pixel size (0.35 arcsecl the telescope and will serve as input tasks using a few words only: as such it pixel) on the red channel and is building to the operating manual. We also ob- is hardly exhaustive and it might be un- a CCD camera to be permanently tained astronomical observations for fair to a few. mounted at the other nasmyth focus illustrative or scientific purposes and If someone discovers himself for- (pixel size about 0.1 arcsec) to exploit four examples are shown in Figures 4 gotten, would he please blame the the windows of exceptional seeing through 6. stress of 20 days and nights of commis- (hopefully down to about 0.3 arcsec The analysis of the first EMMl obser- sioning and forgive me. All have to be FWHM). vations has just started but the prelimi- praised for their skill, patience and care: nary reductions confirm that EMMl is up they managed very well indeed. A spe- to or better than the target specifica- cial, personal thank-you goes to Hans Examples of Astronomical tions (see e.g. the limiting magnitudes in Dekker for overseeing the project with Observations Table4 of the 1986 paper quoted an optimism which fortunately is supe- The commissioning period in June- above). The combination NTT-EMMI is rior even to mine and to Jean-Louis July was centred on the full moon and likely to become a powerful tool for a Lizon for the infinite numbers of hours plagued by the first heavy rain of the wide range of astronomical pro- that he has spent in Garching and at La year. It was however still possible to grammes. Good luck to the future ob- Silla carefully dealing with EMMl's 29 collect a number of astronomical obser- servers! functions, one by one and together.

New 2 D IR Array Detectors for Imaging and Spectroscopy at ESO A. MOORWOOD, ESO

The lack of recent news in export approval, is not a trivial exercise results of these efforts. The most con- the Messenger may have created the by any means. In addition to our on- crete is the delivery of an engineering impression among some infrared obser- going negotiations with Philips Compo- and the first of two 58 x 62 lnSb science vers that perhaps not much has been nents for a replacement 64 x 64 grade arrays from the Santa Barbara going on in Garching to upgrade the Hg : Cd : Te array for IRAC, therefore, Research Center whose procurement performance of the infrared instrumen- we have also been in contact since early started with our request for quotation in tation on La Silla since IRAC was offered in 1989 with several other major detec- January 1989 and is illustrative of the in April 1989. In fact, this has been a tor manufacturers with the aim of pro- leadtime involved in obtaining such de- period of particularly intense activity curing 2 D IR array detectors for the vices. Exhibiting dedication beyond the aimed at expanding our infrared upgrade of IRSPEC at the NTT and to call of duty, Gert Finger braved 50 "C capabilities on La Silla in several areas equip the new IRAC 2 cameras being heat during one of the worst forest fires considered to be both of immediate sci- developed to accommodate 256 x 256 in Californian history to collect the latter entific interest and important prepara- format arrays. During the same period at the beginning of July. Only a few days tory steps on the road to implementing we have also been developing a new later, during a visit to Garching by Dr. K. the VLT instrumentation plan. Our over- VME based acquisition system capable Vural, head of the Imaging Devices Divi- all aim is to provide La Silla with first of handling the various different readout sion of the Rockwell Science Center, class imaging plus some low resolution schemes and formats anticipated, ex- we were able to draw up the techni- spectroscopic capabilities throughout panding our laboratory test facilities, de- cal specifications for a 256 x 256 the infrared from 1 ym to - 17 pm plus signing and tendering for the IRAC 2 Hg : Cd : Te array whose procurement an upgraded IRSPEC for 1-5 pm cameras, preparing for the transfer of had been approved by the STC and medium resolution long slit spectros- IRSPEC to the NTT and finalizing the Finance Committee in May. Towards the copy before we reach the period of peak technical specification of a 10-pm cam- end of July, in fact about a month after effort required on the VLT instrumenta- era/spectrometer to be built in collab- the effective kick off following the pre- tion. This is an ambitious goal, at the oration with the Service d'Astrophysi- liminary design review, the contract for limit of our resources, and a key element que, CEN, Saclay. the 10-pm camera was signed at Sac- is of course the procurement of high Following a number of events within lay. One disappointment has been the performance array detectors which, giv- the space of a few weeks around the fact that we have been unable so far to en the rapid evolution in this field, their end of June and early July it is now replace the 64 x 64 Hg : Cd : Te array in high cost and the need to obtain import/ possible to report here some positive IRAC both to offer improved perfor- mance to visitors and to avoid conflict TABLE 1: IRSPEC Characteristics with our other projects which are com- I I I peting for the same limited manpower Wavelength range 1-5 (L~rn) resources. Although the formal contrac- Pixel size 2 (arcsec.) tual delivery date (end July) had not Slit length 2 (arcmin.) expired at the time of writing, Philips Gratings No. 1 300 I/mm, No. 2 600 I/mm Components had initially hoped to deliv- er earlier and we have thus been in a Resolving power 1 300-3000 (2 pixels) state of readiness to test and install the Detector array on La Silla for several months. Quantum efficiency 0.89 (2.85 Ltm) Although several uncertainties in our Operable pixels 99.6 % overall programme still remain therefore, Read noise 350 e the prospects for substantially improved Dark current (35 K) 100 e/s infrared spectroscopic and imaging Well capacity 1 E6e capabilities on La Silla are currently looking good and this is an appropriate Overall point source sensitivity 5-10 gain below 3 pm (TBD) time to review their anticipated availabil- ity in order to give the community time to prepare for them. wavelengths and requires cooling to both its overall sensitivity and photomet- - 10 K to avoid dark current limitations. ric accuracy. Nevertheless, even if not IRSPEC Upgrade At present, therefore, it is planned to with the planned performance, this new At the time of its installation at the install either the SBRC array already in- capability on La Silla has produced new 3.6-m telescope towards the end of house or the second to be delivered in scientific results and provided valuable 1985, IRSPEC was the first instrument September. Table 1 summarizes the observational experience. of its type to be equipped with a self- main instrument characteristics ex- pected with this array, which has 76-ym scanned monolithic array detector. Dur- IRAC 2 ing Period 46 (October 1990-April pixels compared with 200-pm in the 1991) it is now planned to both transfer present linear array, together with the The IRAC 2 camera under develop- IRSPEC to the NTT and to upgrade it by array performance data supplied by ment in Garching is similar in concept to replacing its present linear array with a SBRC but which we have yet to confirm IRAC at the 2.2-m but provides a larger 2 D lnSb array. At the NTT the instru- by our own tests. field (- 3 arcmin.) and is designed to ment will be permanently attached to accommodate arrays of 256 x 256 pix- els which have just recently become the telescope structure at one of the lRAC Nasmyth foci and will therefore not be available. It will be equipped with stan- subject to flexure effects. An optical de- For more than 18 months now we dard broad-band filters, narrow-band rotator installed between the slit and the have been faced with the problem of filters, a K-band scanning Fabry Perot telescope adapter will be used to com- replacing the 64 x 64 Hg : Cd : Te array etalon for imaging spectroscopy at pensate for field rotation, TV slit viewing from Philips Components which was R - 1000 and typically 5 selectable im- will be retained and an integrating unfortunately damaged accidentally at age scales in the range -0.1 -2 arcsecl sphere equipped with a black body plus La Silla before it could be offered to pixel depending on the array installed continuum and spectral line lamps lo- visitors. First test images with this array and the telescope (2.2- or 3.6-m). Actu- cated in the adapter will be available for had been promising despite a rather ally, two cameras are being built with internal calibration. large number (- 10%) of "hot" pixels, the idea originally of keeping one in Replacement of the present 1 D array and its large well capacity was particu- Garching to provide the flexibility of up- with a 2D array will provide a new long larly attractive for imaging in the thermal grading the array as and when possible slit capability, higher resolving power, infrared longward of 3 km (Moorwood, and then exchanging with the one of La better sampling, improved sensitivity Finger and Moneti, The Messenger, 54, Silla. As noted above, negotiations are and should substantially reduce the 56 (1988)). In fact, this was an experi- now proceeding with Rockwell for the problems of object centring and sub- mental device still on loan from Philips supply of a 256 x 256 Hg : Cd : Te array spectrum curvature (the so-called who kindly agreed to write off its loss at which, on the basis of our discussions "vignetting") experienced at the 3.6-m their expense and to accept an im- so far could probably be delivered at the telescope. The scientific performance proved and more formal specification earliest by the middle of next year pro- and versatility of the instrument for its replacement. This nevertheless viding the necessary export approval should therefore be considerably en- took time and, subsequently, technical can be obtained. This array will have a hanced. problems appear to have arisen in some long wavelength cutoff at 2.5 ym and its Both the SBRC 58 x 62 and the more of the development work undertaken to outstanding features are its large format recently developed Cincinnati Elec- achieve our new specification. It has plus extremely low read noise and dark tronics 64 x 64 element lnSb 1-5.6-ym consequently not proved possible to ob- current (values of 20 e and < 1 e/s re- arrays have been considered for the up- tain this array as quickly as appeared spectively have been achieved with al- grade. A prototype array on loan from possible initially although it is still ex- ready existing arrays) which are more Cincinnati Electronics has already been pected at any time and will be installed on than sufficient to ensure background tested in Garching and is the first device La Silla as soon as possible. In the mean- limited performance in all the modes to be operated with our newly de- time the camera is still available with its foreseen for IRAC 2. In addition to mak- veloped acquisition system. The actual 2.3 Km cutoff 32 x 32 array which had ing the array available to the community array tested could be excellent for the been supplied by Philips initially only for as soon as possible, however, we have thermal part of the IRSPEC range but, dark current tests and was not intended an additional interest in evaluating it for as known in advance, exhibits a large for operational use due to its smaller the "short" wavelength channel of the drop in quantum efficiency at the shorter format and low filling factor which limits VLT Medium Resolution IR Spectrome- terllmager to be built by ESO (Moor- 10-pm CameraISpectrometer which is a larger format version of the wood and Delabre, 1990, ESO Techni- (TIMMI) array developed for the Infrared Space cal Preprint No. 13 - to appear in Pro- Observatory but with a larger well ceedings of SPlE Conference 1235). This is a new instrument for the capacity to handle the higher Both lnSb and Hg : Cd : Te arrays of this 2.243.6-m telescopes to be developed, background levels experienced in size and sensitive out to 5 ym are also as mentioned above, in collaboration groundbased use. TlMMl will provide for under development and of obvious in- with the Service dlAstrophysique, Sac- broad- and narrow-band imaging in the terest for the second IRAC 2 and for the lay, with an additional contribution from 10-b~mwindow and probably out to the long-wavelength channel of the VLT the Observatoire de Lyon. Again, in ad- short-wavelength end of the 20-ym win- Spectrometerllmager. In the meantime dition to providing a new observational dow and for grism spectroscopy at re- it is still planned to restore the L (3.8 ym) capability on La Silla, this instrument is solving powers of several hundred. First capability of IRAC as soon as possible intended to provide technical feedback tests on La Silla are foreseen for April and, depending if and when we actually and observational experience in prepa- 1992 and a more detailed description of receive the Rockwell array, to consider ration for the VLT. In particular it is of this instrument together with the mean- equipping one of the IRAC2 cameras interest to evaluate the 64 x 64 Ga : Si ing of its acronym will appear in a future with the second of our 58 x 62-element detector array to be supplied by LETIl issue of the Messengerwhen the project SBRC arrays. LIR in Grenoble for this camera and is more advanced.

The ESO MAMA Detector M. CULLUM and E. J. WAMPLER, ESO

Introduction beginning of the run the detector Despite the fact that CCD # 8 has For some time ESO has been in- suffered damage to the anode array rather good sensitivity in the near ul- terested both in improving the perfor- which reduced the available size of the traviolet, there is no question that the mance of the ESO detectors in the UI- detector format. After the observing MAMA gave a better signallnoise ratio traviolet spectral region, and in develop- session the detector was returned to than did the CCD for faint objects at ing a working pulse counting detector, Munich and then to the manufacturers, wavelengths less than h4200 A. Be- similar to the IPCS. A working MAMA Ball Aerospace Systems Group, for in- cause the MAMA count rate limitation pulse counting detector equipped with a spection and evaluation. A second run translates to very long calibration ex- low dark current, UV sensitive, bi-alkali with the same detector took place in posures, and because we do not yet photocathode is now available to the La early March, 1990. Because it has not have very much information about the Silla user community. It offers good UV yet proved possible to repair the dam- stability of the MAMA detector, it is not sensitivity, freedom from readout noise aged anode array, the tube in use on La possible to compare the performance of and cosmic ray events, real time Silla still suffers from a number of defec- the two detectors for high signallnoise monitoring of the accumulating signal tive anodes that reduced the size of the ratio spectra', or for objects that have a and excellent linearity for faint sources. detector field of view available. Here we high flux rate. The brightest magnitude For observations of faint sources with describe our experience with the MAMA that can be observed with the MAMA/ high resolution spectrographs i! the attached to CASPEC on the 3.6-metre CASPEC configuration without attenua- spectral interval hh3000 !4 - 4000 A, the telescope. tion is about mu = 8. Because of the MAMA detector is more than competi- encoded nature of the MAMA readout, tive with the present ESO CCDs and is the defective anode spoiled a band of CASPEC Observations with therefore the detector of choice for ul- columns 64 pixels wide situated to- MAMA traviolet CASPEC or the CES observa- wards one end of the detector field (see tions. The MAMA detector was shipped to Fig. 1). Because we did not want to In common with other pulse counting Chile in February 1989 and attached to bridge the defective pixels in the data detectors, the device saturates with CASPEC at the end of the month for a reduction process, we used the MAMA bright sources. This translates into a 6-night engineering run. On the after- with the Short Camera and 79 grlmm requirement for long integration times noon of the first day, while the tube high echelle so that a complete order could for the flat field exposures needed to voltage was slewing, the anode array be recorded in the undamaged area. remove the pixel-to-pixel variations in suffered an electrical failure that phys- This resulted in a somewhat undersam- detective efficiency. But, unlike the CCD ically broke the connection to one of the pled spectrum since the MAMA has detectors, long dark exposures are not anodes and destroyed about 40 transis- 25 pm pixels as compared to the 15 km needed to define the background. tors in the associated pre-amplifiers. It pixels of the CCD. If the MAMA detector The < 1 psecond temporal resolution took two days to replace these transis- had the full format available, it would of the MAMA also provides a capability tors. During this time CCD # 8, the stan- have been possible to use the CASPEC for future activities involving high time dard CCD for CASPEC, was mounted Long Camera to have obtained better resolution observations (speckle, inter- and observations of SN 1987A together matching of the MAMA format to the ferometry, adaptive optics, etc.) for with several quasars were made. After optical format of CASPEC. This option which ESO has no other suitable detec- the MAMA was repaired, it replaced the would have reduced the spectral cov- tor available. CCD and the observations of the Super- erage of the spectroscopic system. In late February, 1989, the MAMA de- nova and the quasars were repeated. tector was mounted on CASPEC where Thus, it was possible to make a direct ' It should be remembered that photon-counting its performance was directly compared performance comparison between this detectors are normally not optimum for high SNR to that of ESO's #8 RCA CCD. At the RCA CCD and the MAMA. applications. From a cosmetic point of view, the during the long integration. Blue light MAMA is comparable to CCD # 8. was used to centre the quasar. Evenly spaced across the detector for- With the Short Camera, the MAMA mat, a number of individual vertical col- detector showed a rather larger point- umns showed about 20 % less response spread function than it showed in the than their neighbours. However, typical laboratory in Garching. However, be- differences between adjacent columns cause the resolution obtained with the is +5%. Similar behaviour exists also Long Camera (for which a more suitable for the rows. These characteristics, due field lens was available) was significantly to the discrete nature of the anodes, are better (FWHM - 1 pixel), it seems clear largely cosmetic since they do not sig- that the field lens used for these obser- nificantly influence the detective quan- vations was limiting the MAMA resolu- tum efficiency. The only uncertainty is tion with the Short Camera2. Also, sharp their stability; they will be hard to re- absorption features show increased re- move if they are unstable. During our sidual central intensity in the MAMA runs they proved to be stable in a given spectra when compared to the CCD Figure 1: A flat field image taken with the ESO run, but we do not yet have enough spectra. Possible explanations for this MAMA detector. The spectral range runs experience to prove that they are, in from about A3500 A to A4 100 A. The vertical effect include: the non-optimum field dark stripes to the left of the image and the fact, stable over a long period of time. In lens used, scattered light in the MAMA horizontal dark line that runs from the left to any event, amplitude of the fixed- tube, or due to scattering of photoelec- the centre of the image are due to defective pattern modulation was greatly reduced trons in the tube. Again, the use of the anodes within the tube. Ultraviolet wave- after the detector had been re-op- CASPEC Short Camera taxed the reso- lengths are to the top. timized before the March 1990 observ- lution capabilities of the MAMA detec- ing run. It may be possible to reduce tor. Figures 4-5 illustrate these points. these offsets even further so that they The MAMA has a number of advan- may not be a problem in the future, tages over the CCD. ESO astronomers although this would necessitate chang- will probably find that the chief advan- ing the anode encoding scheme and, tage of the MAMA is that in the UV hence, the current MAMA electronics. spectral interval the MAMA has a higher Figure 2 illustrates the fixed-pattern Detective Quantum Efficiency than any modulation and Figure 3 shows a 5.6- other panoramic detector that has been hour spectrum of the 16-magnitude deployed on La Silla. Another advantage quasar 1101 -264 after division by the is that since the accumulated spectrum flat field. Note that the spectrum is is displayed as the integration proceeds, somewhat wider at far ultraviolet the astronomer can continuously wavelengths than it is in the blue. This is monitor the overall system performance. probably due to the effects of atmo- spheric refraction differentially moving A purpose designed field lens is currently on order the UV spectrum relative to the blue and will be installed in the near future.

Figure 2: An expanded view of Figure 1. The "chicken wire" structure seen in the flat field is due to small gain differences between the different amplifiers.

ol'l'llllllllllllll~IIIIIII 100 200 300 400 500 600 Figure 3: A spectrum of the 16-mag quasar 1101-264. This spectrum has been divided PIXEL by the flat field exposure shown in Fig- Figure 4: A portion of the extracted spectrum of the quasar 1101-264. The scattered light ures 1-2. Note that the response is now very background between the orders has been removed. This results in good scaling of the strong smooth. absorption lines. 79 GR/MM GRATING, ORDER #60 relatively coarse resolution detector. If, 10000 in the future, the full MAMA format be- comes available, the CASPEC Long Camera could be used and the detector pixel size would be better matched to the spectrograph optical resolution. 7500 The present data taking software used with the MAMA does not allow access to IHAP during integrations. The computer zb is therefore not then available to perform 2 other tasks, such as the precise estima- u 5000 tion of the signalhoise ratio of an expo- -4 sure as the integration proceeds, arith- E- 0 metic on previous exposures, computing b the continually changing atmospheric dispersion parameters, etc. The atmo- 2500 spheric dispersion parameters are needed to accurately centre the UV im- age of an object in the slit since the ESO TV cameras detect only the visual image of the object. Because the differential 0 atmospheric dispersion is so large in the 100 200 300 400 500 600 PIXEL UV, the ability to calculate the position angle and amplitude of the dispersion is Figure 5: The Thorium-Argon spectrum. It may be compared with that given in the ESO Atlas of particularly important for a UV sensitive the Thorium-Argon Spectrum (ESO Scientific Report No. 6 - July 1987). detector such as MAMA. Future minor revisions to the data taking software will allow the MAMA detector to be used On-line monitoring of centring errors, resolution, the rotation of the Earth more efficiently. clouds, etc. is possible when the smears long exposures. With the In conclusion, the ESO MAMA is a ratemeter is attached to the detector. MAMA, long exposures of faint objects working detector with particular advan- Because the astronomer can see the can be broken in order to obtain velocity tages for UV observations. A few minor spectrum building up, the object iden- calibrations. The MAMA has a very low modifications presently being underta- tification is obtained early in the obser- dark background (about 0.1 event/pix- ken will make the detector even easier vation, and integration can be halted el-' hour-' at 5C), and it also dis- to use. It thus fills a needed capability in when it is judged that a sufficiently high criminates against the cosmic rays that the instrument compliment of ESO. signal/noise ratio has been obtained. It plague long integrations with CCD de- If there is sufficient user interest in the is therefore very well suited to those tectors. MAMA detector, ESO could purchase problems in which very long exposures The ESO MAMA detector has a some- additional tubes with improved charac- of faint objects are needed. Because what smaller (- 1000 x 250 pixels) for- teristics. We suppose that this will de- there is no readout noise, long ex- mat than the CCDs and the loss of a pend to some extent in the future availa- posures can be broken into short seg- number of pixels leaves one with only bility of improved CCD detectors that ments that are interspersed with calibra- about 670 x 250 contiguous pixels. To could become competitive with the tion spectra. This is a significant advan- achieve overlap of the spectral orders MAMA for the UV applications, as well tage for instruments, such as CASPEC, the short Camera must then be used. as the interest in applications where the that suffer from flexure problems. For This results in a less than optimal map- fast temporal response time of the spectra taken with very high spectral ping of a high resolution image onto the MAMA can be utilized.

Deconvolution of NTT Images of EISO Galaxies F. ZAVA~~I',0. BEND~NELL~~,G. PARMEGGIANI~, G. G.C. PALUMBO',~~~~G. F. B1GNAMl3 ' Dipartimento di Astronomia, Universita di Bologna, Italy. Osservatorio Astronomico di Bologna, Italy. 1. F. C. T. R./C. N. R., Milano, Italy. 1. TE. S. RE./C. N. R., Bologna, Italy.

Introduction The first glimpses of the high quality On the other hand, in recent years a The New Technology Telescope (NT) images obtainable by virtue of the considerable effort has been put into the has recently become fully operational happy combination of advanced tech- development of highly sophisticated and subsequently made available by nology and excellent seeing conditions mathematical techniques to deconvolve ESO to European astronomers in the at La Silla have already been published images in one and two dimensions. standard scheduling procedure. (The Messenger, issues 56 and 58). Although the effects of atmospheric posures are shown, and from Figure Ib where the adopted average PSF from NTT PSF the 5-minute frame is compared with the - S4 1 rnxn most luminous star in the I-minute ex- -1 - average posure image as well as with a star in the field of the galaxy ESO 440 G 37. The average PSF (HWHM -0.34 arc- -2 sec) was fitted with a sum of 3 Gauss- ians (e.g. Bendinelli et al., 1987, 1989) -3 as well as a Moffat (1969) function; the fit parameters are listed in Table I. -4 This comparison brings the conclu- sion that the NIT and the seeing condi-

-5 tions were considerably stable both within each single frame and from one frame to another. -6

-7 The Deconvolution 0 5 1 1.5 2 0 5 1 1.5 2 R (arcsec) R (arcsec) Surface brightness profiles were ex- Figure 1: (a) Brightness profiles of some stars near PKS 1209-52 from 5 and 1 minute tracted using the VISTA code. integration time. (b) Brightness profile of the adopted (average) PSF (solid circles and line) All galaxies in our sample were de- compared with the one of the most luminous star in the I-minute frame (solid line). The dashed convolved by means of three quite diffe- line is the PSF derived from a star in the ESO 440 G 37 frame. rent techniques: - Regularized numerical inversion of the convolution integral equation (RLS), applied to brightness profiles. Such turbulence which produces image blur- era (515 x 31 3 pixels; Nasmyth focus) at method was previously used in the de- ring cannot entirely be abolished in any the ESO NIT telescope in the V band. convolution of a variety of very different image taken with a ground-based tele- The images were acquired on the night of objects (see e.g. Bendinelli et al., 1986 scope, one can aim, deconvolving with January 24, 1990. The typical seeing and references therein). With a PSF ex- the Point Spread Function (PSF), at FWHM was 0.68 arcsec for the duration pressed in terms of Moffat function. "cleaning" the observed image in order of these observations, and the sampling - Regularized Multi-Gaussian (RMG), to approximate the "real" image, as it was 0.246 arcseclpixel (rebinned im- based on the analytical solution of the would be obtained in the absence of the ages). A total of eight CCD frames were convolution integral equation when both atmosphere. This process has been ap- obtained with integration times ranging object and PSF are expressed as a sum plied on various occasions using a vari- from 25 to 21 0 sec. Standard processing of Gaussian functions. ety of deconvolution techniques and of .framesfor flat field and bias was used. This method has two major advan- has been proven to be quite powerful. In this note we discuss the deconvolution tages: There still is a debate, however, on of these elliptical galaxies. (a) it is insensitive to undersampling which mathematical technique works (b). . it runs a whole deconvolution cvcle best. Combining high quality images in a few seconds on a Personal Com- The Point Spread Function with robust deconvolution Drocesses, Duter. one can hope to reach a better under- Star images suitable for PSF extrac- The major limitation of the RMG standing of both the relative power of tion were not available in all frames. Two method, however, is that it is applicable the algorithms used and the goodness frames of the stellar field near PKS only to round or elliptical images and of the images obtained, or, in turn, to 1209-52 (1 and 5 minutes exposure does not work on images lacking test the telescope characteristics. time) were therefore used in order to symmetry. During the first general observer NlT derive an average PSF. Such Point - Deconvolution adopting a method run, a few images of well-known bright Spread Function was used for decon- devised by Hunt (1973) (HUNT). This is a galaxies were obtained in good seeing volving all extended objects in the pres- bidimensional deconvolution and makes conditions by one of us (G. F. 6.). ent sample. The seeing conditions for use of FFT, and basically is a generaliza- The present paper describes the ob- this reference star field were monitored tion of Wiener's filter. As far as we are servation of those objects and the three to be identical to those of the galaxy aware the HUNT method has only been mathematical algorithms used to de- images. applied to astronomical images once by convolve their images. From the results The stability of the star profiles can be Heap and Linder (1987) for deconvolv- obtained, conclusions can be drawn on deduced from Figure 1 a, where some ing the image of SN 1987A. the relative power of the deconvolution stars from both 1 and 5 minutes ex- The three deconvolution methods techniques used, the aualitv. . of the im- ages the NIT is able to acquire and some interesting astrophysical aspects TABLE I: Parameters of the fitted average PSF of the objects studied. FWHM 3-Gaussian fit Moffat fit (arcsec) L,, a,, i = 1, 2, 3 a, B Observations Five EISO galaxies: ESO 440 G 37, 0.306 0.51 8 NGC 31 15, NGC 3585, NGC 3904, NGC 0.115 1.121 3923 were observed. These images were Note: o,,rr in arcsec. obtained using the RCA # 15 CCD cam- . OBS RLS BSO 440 G37 -RUG NCC 3585 - RMC NCC 3904 -RUG -- HUNT - -HUNT - - - PSF - PSF - PSF

- -

-

- -3 - -3 \\ - t -3

-4 ' '1'"1'"1'1'1"' -4 '"l"'J'lll'l'l''l 0 2 4 10 0 2 10 R (arcrec) 4~ (arcrec)

- OBS - RLS NCC 3115-RMC NCC 3923 - RMC - -.HUNT - PSF - PSF

-4-'h'~''f~'''~~~@111~ 0 2 I 8 8 I0 R (arersc)

Figure 2: Observed (solid dots) and deconvolved (lines) profiles of the five galaxies. Observed PSFprofiles, normalized to the central brightness of the galaxies, are also shown as solid lines and dots.

listed above are compared on the same Discussion of the Results ment that with these images (i.e. pixel image here for the first time although the size, object size, PSF) all three methods first two (RLS and RMG) were discussed Table II should be regarded as the work equally well. in Bendinelli et al. (1990). main result of this work which goes to- This means that the unambiguous Table II gives some of the relevant ward the analysis of core structure of identification of a "point" mass in the parameters of the deconvolutions: ob- early type galaxies, as outlined in Ben- centre of nearby galaxies, if present, is served and deconvolved HWHM, in arc- dinelli et al. (1990). possible by a variety of methods, if well- sec, for the different methods and the Differences among the deconvolution sampled data are available. This central difference in observed and deconvolved methods are of the order of some per mass concentration with higher mass- central surface brightness. cent, small enough to justify the state- to-light ratio than the stars that appear If a gain in resolution is defined as the ratio between the HWHM of the ob- served and deconvolved profiles, then TABLE II: Parameters of the deconvolved profiles from this table values can be derived ranging from 1.3 to 3.7, depending on Galaxy OBS RLS RMG HUNT the relative dimension of galaxy and HWHM HWHM Ah HWHM ALL HWHM Ay PSF. In Figure 2 observed and decon- E 440 G 37 0.75 0.42 0.73 0.38 0.80 0.40 0.86 volved profiles of the five galaxies are NGC 3585 0.88 0.40 0.71 0.24 0.82 0.49 0.70 presented. NGC 3904 0.90 0.52 0.59 0.50 0.59 0.57 0.58 The results do not depend on the NGC 3115 1.07 0.48 0.60 0.43 0.66 0.58 0.60 functional form choosen for the PSF NGC 3923 2.27 1.80 0.18 1.80 0.1 8 1.74 0.22 representation, confirming previous Note: HWHM in arcsec; Ap = (observed-deconvolved) in mag/arcsec2. tests (Bendinelli et al., 1988). Figure 3: NGC 31 75-50 galaxy; BT = 9.75. Figure 4: NGC 3585, also ESO 502 G 25-E Figure 5: ESO 440 G 37-E-SO galaxy; Bo = Left panel: original CCD frame (1 .'7 x O,'9). galaxy; Bo = 11.40. Left panel: original CCD 14.30. Left panel: original CCD frame Right panel: Hunt deconvolution. frame (1 .'7 x 0.'9). Right panel: Hunt decon- (1 .I7 x O.'9). Right panel: Hunt deconvolution. volution. to dominate in any tested object the be regarded as a step forward towards Bendinelli, O., Parmeggiani, G., and Zavatti, galaxy mass distribution on scales of the understanding of galaxies them- F.: 1988, J. Astrophys. Astron. 9, 17. tens to hundreds of parsec has tenta- selves and the existence of black holes Bendinelli, O., Parmeggiani, G., and Zavatti, tively been identified with a black hole in their centres. F.: 1989, in Highlights of Astronomy, proc. by many authors. This work was supported in part by 20th IAU General Assembly, in press. Dor- drecht: Kluwer. the Minister0 della Pubblica lstruzione The debate on the presence of black Bendinelli, O., Parmeggiani, G., Zavatti, F., holes in the centre of galaxies is still and Osservatorio Astronomico di and Djorgovski, S.: 1990, Astron. J. 99, quite open since the data seem only to Bologna. 774. imply that some additional mass is re- Gouiffes, G., Wampler, E.J., Baade D., and quired on rather small scales in the References Wang, L.-F.: The Messenger, 58, 11. centre of galaxies. Heap, S.R., and Linder, D.J.: 1987, Astron. Bendinelli, O., Parmeggiani, G., and Zavatti, Astrophys. 185, L 10. Hence any deconvolution method F.: 1986, Ap. J. 308, 61 1. Hunt, B.R.: 1973, IEEE Trans. Comp., C-22, which will permit to constrain the mass Bendinelli, O., Parmeggiani, G., Piccioni, A., 805. distribution in the core of galaxies may and Zavatti, F.: 1987, Astron. J. 94, 1095. Moffat, A.F.J.: 1969, Astr. Ap., 3, 455.

MlDAS Memo ESO Image Processing Group

ments and developments of new appli- states that MlDAS is the image process- 1. Application Developments cation programmes in MIDAS. Not only ing system of ESO to be used both for The main efforts were placed on vali- will this make it possible to have new off-line data reductions and for on-line dation of basic MlDAS commands and algorithms and applications included evaluation of data from ESO telescopes the subsequent correction of problems into MlDAS after a period of limited im- including the VLT. MlDAS is available to reported. Since the next major release provements in this area, but will spread all non-profit research organizations. 90 NOV will be frozen in September al- long-term, detailed knowledge of Such organizations must sign a User ready, only a limited number of these MlDAS in the community when people Agreement with ESO before obtaining improvements will be available in that in these positions return to their home the package. This agreement will reg- release. institutes. ulate the usage of MlDAS and ensure The COPY/DISPLAY command which In addition to these positions, it will be that it is not exploited commercially. can produce hard copies of the image possible to invite people who have This policy will be implemented as of the display has been upgraded to be able to made interesting algorithms and pro- 90 NOV release of MIDAS. provide output for colour Postscript grammes, to ESO for an implementation printers. This makes it possible to get of them into the MlDAS environment. 4. MlDAS on New Systems good working hard copies in both BAN People interested in contributing and/or and colour directly from the image dis- making new applications to MlDAS may The 90 MAY release of MlDAS was play in MIDAS. contact the IPG with detailed descrip- installed on an IBM System 6000 Model tions. 540 (the new RlSC CPU) made available by IBM. Only very mino; problems were 2. New Positions detected, all relating to the operating 3. Distribution Policy Two additional short-term positions system AIX 3.1 which was a preliminary (with durations of up to two years) have The ESO Council, during its last meet- version during the tests. Those prob- been allocated to the MlDAS group. ing in June 1990, defined the policy for lems have been resolved in the official They will be used mainly for improve- usage and distribution of MIDAS. It release of AIX 3.1. The system had an .... XI1 display manager and could be used EARN:MIDAS@?DGAES051 .y2L: ' , :*b4 ESO, the European Southern Observa- directly 'for image display and graphics SPAN:ESO::MIDAS . W$$ tory, was created in 1962 to ...establish with MIDAS. The configuration included FAX.: 149-89-3202362; a&.: MlDAS ' .{:;!': and operate an astronomical observa- ' -. u :-\ HOT-LINE I' tory in the southern hemisphere, equip- 128 Mb of memory which made it ped with powerful instruments, with the I difficult to judge the disk I/O perfor- Tlx.: 52828222 eo d, aim of furthering and organizing collabo- mance. The system gave a very good HOT-LINE ration in astronomy. .. It is supported response with MlDAS benchmarks indi- Tel.: + 49-89-32006-456 by eight countries: Belgium, Denmark, cating a performance in the order of 3 ... . u.. .4 .. France, the Federal Republic of Ger- times faster than other workstations. many, Italy,theNetherlands, Swedenand Users are also invited to send us any :'*& Please note that the mentioning or suggestions or comments. Although we Switzerland. It operates the La Silla ob- testing of specific computer systems is servatory in the Atacama desert, 600 km I do provide a telephone service we ask not in any way an endorsement. ' - north of Santiago de Chile, at 2,400 m 3. users to use it only in urgent cases. To altitude, where fourteen optical tele- I make it easier for us to process the I 5. MlDAS Hot-Line Service - scopes with diameters up to 3.6 m and a requests properly we ask you, when -22 15-m submillimetre radio telescope The following MlDAS support services possible, to submit requests in written .; ';I";. (SEST) are now in operation. The 3.5-m can be used to obtain help quickly when form through either electronic networks, z': New Technology Telescope (Nm has -A . ., ~ a telefax or telex. , recently become operational and a problems arise: '. ' , -* . 1 . giant telescope (VLT=Very Large Tele- - + . scope), consisting of four 8-m tele- ... - ,-.j4@ scopes (equivalent aperture = 16 m) is $;., *: I.: .. under construction. Eight hundred scien- ' +' Contents -. . 4 .$+"? tists make proposals each year for the ,.. use of the telescopes at La Silla. The ESO Portugal and ESO Sign Cooperation Agreement ...... 1 $2 Headquarters are located in Garching, Speech by Professor Jose Pedro Sucena Paiva ...... 2 ., near Munich, FRG. It is the scientific- Speechby ProfessorTeresaLago ...... technical and administrative centre of M.T. Lago: A Short Summary of Astronomy at "Centro de Astrofisica da ESO, where technical development pro- Universidade do Porto" ...... grammes are carried out to provide the New ESO Scientific Preprints (June -August 1990) ...... La Silla observatory with the most ad- ESO Fellowships 1991 - 1992 ...... vanced instruments. There are also ...... extensive facilities which enable the Visiting Astronomers (October 1,1990 -April 1,1991) scientists to analyze their data. In Eu- M. Veron-Cetty and D. Baade: During 2nd ESO/OHP Summer School in rope ESO employs about 150 internatio- Astrophysical Observations: Observatoire de Haute-Provence Becomes a nal Staff members, Fellows and Asso- European Northern Observatory ...... ciates; at La Silla about 40 and, in addi- Selection of the VLT Site ...... tion, 150 local Staff members. M. Grenon: The Northern Chile Climate and Its Evolution. A Pluridisciplinary Approach to the VLT Site Selection ...... D. Enard: Progress on the VLT Mirror Cell Design ...... R.M. West: Halley Enters Hibernation ...... The ESO MESSENGER is published four Minor Planet Named After Lo Woltjer ...... times a year: normally in March. June, T. Le Bertre et al.: Profile of a Key Programme: Investigation of the Galactic September and December. ESO also publishes Conference Proceedings, Distribution and Physical Properties of Carbon Stars ...... Preprints. Technical Notes and other H. Hensberge et al.: Profile of a Key Programme: High Precision Radial Velocity material connected to its activities. Determinations for the Study of the Internal Kinematical and Dynamical Press Releases inform the media about Structure and Evolution of Young Stellar Groups ...... particular events. For further informa- P. Benvenuti: The Status of the Hubble Space Telescope ...... tion, contact the ESO Information Servi- R.N. Wilson: "Matching Error" (Spherical Aberration) in the Hubble Space 1 ce at the following address: Telescope (HST): Some Technical Comments ...... EUROPEAN D. Baade and L. B. Lucy: HST Images: What Can Image Processing Do? ...... SOUTHERN OBSERVATORY A. Blaauw: ESO's Early History, 1953-1975. VIII. The 3.6-m Telescope Project; Karl-Schwarzschild-Str. 2 From Concept to the Late 1960's ...... D-8046 Garching bei Munchen M. Scardia: Observations of Visual Double Stars at La Silla ...... Fed. Rep. of Germany P.S. The and E. Bibo: Long-term Photometry of Herbig Ae/Be Stars in the Tel. (089) 32006-0 StromgrenSystem ...... Telex 5-28282-0 eo d M. Della Valle and T. Augusteijn: The 1990 Outburst of VY Aqr ...... Telefax: (089) 3202362 Bitnet address: IPS61 DGAES051 P. Andreani, A. Franceschini and J. Roland: 1.2-mm Continuum Observations of IRAS Galaxies: Implications for Gas Mass and Cold Dust Component ... M. Hawkins and P. Vbon: Variability as a Way to Find Quasars: a Complete Sample ...... The ESO Messenger: StaffMovements ...... Editor: Richard M. West D. Baade and P. Crane: A Search for Interstellar Be II h 3130: CASPEC Shakes Technical editor: Kurt Kjar Hands With IUE and GHRS ...... Printed by Universitats-Druckerei First Announcement of the 3rd ESO/ST-ECF Data Analysis Workshop ...... Dr. C. Wolf & Sohn S. D'Odorico: EMMI, the ESO Multi-Mode Instrument, Successfully Installed at HeidemannstraOe 166 theNV ...... 8000 Munchen 45 A. Moorwood: New 2D IR Array Detectors for Imaging and Spectroscopy at Fed. Rep. of Germany ESO ...... M. Cullum and J. Wampler: The ESO MAMMA Detector ...... ISSN 0722-6691 F. Zavatti et al.: Deconvolution of Nl7Images of WSO Galaxies ...... ESO Image Processing Group: MlDAS MEMO ......