OBSERVER’S HANDBOOK 1988 EDITOR: ROY L. BISHOP THE ROYAL ASTRONOMICAL SOCIETY OF CANADA CONTRIBUTORS AND ADVISORS A l a n H. B a t t e n , Dominion Astrophysical Observatory, 5071 W. Saanich Road, Victoria, BC, Canada V8X 4M6 (The Nearest Stars). L a r r y D. B o g a n , Department of Physics, Acadia University, Wolfville, NS, Canada B0P 1X0 (Configurations of Saturn’s Satellites). T e r e n c e D ic k i n s o n , Yarker, ON, Canada K0K 3N0 (The Planets). D a v id W. D u n h a m , International Occultation Timing Association, P.O. Box 7488, Silver Spring, MD 20907, U.S.A. (Lunar and Planetary Occultations). A l a n D y e r , Edmonton Space Sciences Centre, 11211-142 St., Edmonton, AB, Canada T5M 4A1 (Messier Catalogue, Deep-Sky Objects). F r e d E s p e n a k , Planetary Systems Branch, NASA-Goddard Space Flight Centre, Greenbelt, MD, U.S.A. 20771 (Eclipses and Transits). M a r ie F id l e r , 23 Lyndale D r., Willowdale, ON, Canada M2N 2X9 (Observatories and Planetaria). V ic t o r G a i z a u s k a s , C h r is t ie D o n a l d s o n , T e d K e n n e l l y , Herzberg Institute of Astrophysics, National Research Council, Ottawa, ON, Canada K1A 0R6 (Solar Activity). R o b e r t F. G a r r is o n , David Dunlap Observatory, University of Toronto, Box 360, Richmond Hill, ON, Canada L4C 4Y6 (The Brightest Stars). Ia n H a l l id a y , Herzberg Institute of Astrophysics, National Research Council, Ottawa, ON, Canada K1A 0R6 (Miscellaneous Astronomical Data). W il l ia m H e r b s t , Van Vleck Observatory, Wesleyan University, Middletown, CT, U.S.A. 06457 (Galactic Nebulae). H e l e n S. H o g g , David Dunlap Observatory, University of Toronto, Box 360, Richmond Hill, ON, Canada L4C 4Y6 (Foreword). B a r r y F. M a d o r e , David Dunlap Observatory, University of Toronto, Box 360, Richmond Hill, ON, Canada L4C 4Y6 (Galaxies). B r ia n G. M a r s d e n , Smithsonian Astrophysical Observatory, 60 Garden St., Cambridge, MA, U.S.A. 02138 (Comets, Asteroids). Ja n e t A. M a t t e i , American Association of Variable Star Observers, 25 Birch St., Cambridge, MA, U.S.A. 02138-1205 (Variable Stars). R o b e r t L. M il l i s , Lowell Observatory, Mars Hill Road, 1400 West, Flagstaff, AZ, U.S.A. 86001 (Planetary Appulses and Occultations). P e t e r M. M i l l m a n , Herzberg Institute of Astrophysics, National Research Council, Ottawa, ON, Canada K1A 0R6 (Meteors, Fireballs and Meteorites). A n t h o n y F. J. M o f f a t , Departement de Physique, Universite de Montreal, Montreal, PQ, Canada H3C 3J7 (Star Clusters). Jo h n R. P e r c y , Erindale College and Department of Astronomy, University of Toronto, Toronto, ON, Canada M5S 1A1 (Sky Month by Month). P. B l y t h R o b e r t s o n , Earth Physics Branch, Energy, Mines and Resources Canada, Ottawa, ON, Canada K1A 0Y3 (Meteorite Impact Sites). A k io S e n d a , International Lunar Occultation Centre, Geodesy and Geophysics Division, Hydrographic Department, Tsukiji-5, Chuo-ku, Tokyo, 104 Japan (Total and Grazing Lunar Occultations). K e n T a p p i n g , Herzberg Institute of Astrophysics, National Research Council, Ottawa, ON, Canada K1A 0R6 (Radio Sources). Jo s e p h F. V e v e r k a , Centre for Radiophysics and Space Research, Cornell Uni­ versity, Ithaca, NY, U.S.A. 14853 (Planetary Satellites). C h a r l e s E. W o r l e y , U.S. Naval Observatory, Washington, DC, U.S.A. 20390 (Double Stars). PRINTED IN CANADA BY THE UNIVERSITY OF TORONTO PRESS OBSERVER’S HANDBOOK 1988 EDITOR ROY L. BISHOP EIGHTIETH YEAR OF PUBLICATION © THE ROYAL ASTRONOMICAL SOCIETY OF CANADA 136 DUPONT STREET, TORONTO, ONTARIO M5R 1V2 ISSN 0080-4193 THE CENTENNIAL OF THE NGC The initials “NGC” have appeared in many thousands of astronomical papers, including several pages of this edition of the Observer's Handbook, and will continue to do so for decades or centuries to come. Occasionally they even appear in newspapers when an important event such as a supernova bursts forth in a distant galaxy. It is natural then that astronomers are frequently asked “What does NGC stand for?” The answer is easy. It is “New General Catalogue”, compiled and published in 1888 by the remarkable astronomer J. L. E. Dreyer by invitation of the Royal Astronomical Society. The New General Catalogue of Nebulae and Clusters of Stars contains 7840 items, and its supplements, the first Index Catalogue (IC) in 1895, 1529, and the Second Index Catalogue in 1908, 3857, for a total of 13 226. These three catalogues were reprinted in 1953 by the Royal Astronomical Society in its Memoirs series, by the Replika Process by Lund Humphries, London. In 1973 the NGC was republished in revised and altered form by Jack W. Sulentic and William G. Tifft of the University of Arizona at its Press, as The Revised New General Catalogue of Nonstellar Astronomical Objects (RNGC) with corrections and updating of information. Whereas the editions of the NGC are now very scarce, copies of the RNGC may be found in many astronomical libraries around the world. It has been estimated that about 85% of the items listed in it are galaxies. The cataloguing of the nebulous spots in the sky really began in a haphazard way in the 18th century. Charles Messier earned himself long-lasting fame by making a list of 103 nuisance spots that got in his way when he was trying to discover new comets. The last discoveries on his list were made with the help of Pierre Mechain. William Herschel was more thorough and his systematic survey published in three separate catalogues between 1786 and 1802 as a General Catalogue contained some 2500 objects. It was supplemented and expanded to the southern sky by his son John Herschel who published in 1864 the General Catalogue of Nebulae and Clusters of Stars, containing 5079 items. Then in 1888, at the invitation of the Royal Astronomical Society, John Louis Emil Dreyer published the New General Catalogue of Nebulae and Clusters of Stars. The reason for the name is obvious. Dreyer had spent the previous two years checking and systematizing the mass of data, including observations of his own, which had accumulated up to that time. Besides giving accurate positions, Dreyer developed a neat, compact way of describing the nature of the objects in his Catalogues, with pages at the end of interpretation. In particular his use of exclamation marks seems to carry his own enthusiasm over into the reader. Here is part of his description of the Great Globular Cluster in Hercules, one of the distant starry objects most often viewed by amateur astronomers (The full description includes right ascension and north polar distance, both for epoch 1860.0, and the annual precession in these coordinates): No. G.C. J.H. W.H. Other Observers Summary Description 6205 4230 1968 Hailey 1714, ! ! O , eB, vRi, vgeCM, st 11. M 13 with a short section of his explanation. eB = extremely bright; vRi = very rich; vgeCM = very gradually extremely compressed in the middle. The RNGC has translated some of these symbols into modem computer print-out. 2 Dreyer was bom in Copenhagen, Denmark on February 13, 1852. At age 14 he became keenly interested in astronomy when he read a book about the famous Danish astronomer Tycho Brahe. Dreyer began his studies at Copenhagen University in 1869 and by 1870 he had been given a key of access to its Observatory (a happy event which in various locations has befallen other budding astronomers). In 1874 he moved to Ireland where he remained until his retirement. First he worked at Bin- Castle, Lord Rosse’s Observatory, and then at Dunsink Observatory of the University of Dublin. In 1882 he became Director of the Armagh Observatory where he remained until his retirement in 1916 to Oxford and its University. There he maintained his publications until his death on September 14, 1926. Not only did Dreyer complete these great catalogues which would be a creditable life work for anyone, but he also did outstanding historical writing in astronomy. In fact, various astronomers appraising Dreyer’s work differ in their opinions as to which were more important, his catalogues or his contributions to the history of astronomy. (The difference probably comes from the individual’s own interests!) When Dreyer was awarded the Gold Medal of the Royal Astronomical Society (London) in 1916, it was on the basis of this double aspect of his scientific work. The President of the Society, Prof. R. A. Sampson, noted that the award was “for his Contributions to Astronomical History and for his Catalogues of Nebulae”. Dreyer was a principal contributor to the “History of the Royal Astronomical Society” (1923), and he prepared an edition of the complete works of William Herschel. Only two years after he had finished the NGC he published an outstanding volume, Tycho Brahe—A Picture of Scientific Life and Work in the Sixteenth Century.