sign in sign up
<<
Home , Observatory

arXiv:astro-ph/9902030v2 2 Mar 1999 h os fWso,wihicue library a included which Wisdom, called of Baghdad House or- the in academy He scientific AD). a al-Mam¯un, the (813-833 ganized of caliph reign Abbasid the seventh build- during observatory began of ing in- tradition and the encouraged knowl- highly tertwined, wherein were piety context, and city this edge de- large Within and a a sensible and sirable. In considered university, was a library possible. hospital, public if a Greeks of it, existence the to the of add knowledge to the Is- and medieval preserve in to motivation lam strong a Islam was There in Observatories 2 carried not observatories were at efforts his- out their and interest, scientific torical of observations many Mayans and made Greeks Britons, evolve. neolithic they Chinese, how or sky, describe the in that located theories be for to basis a what as can used which be composition lu- chemical motions, or Observatories positions, minosities, celestial one. on incidental data gather an just not a ity, at work reck- The fide time bona calendar. of their the keeping purposes understanding and for oning of or purpose nature, physical the ob- for celestial sys- jects of observation the regular to and dedicated tematic in- institution building, or a stallation, is observatory astronomical An Introduction 1 hl ocnrt nisaltosta eein- be were to that tended installations on concentrate shall hl h nin gpin,Babylonians, Egyptians, ancient the While Observatories hs eeta oisae hr hyare they where are, bodies celestial these bevtr osiue anactiv- main a constitutes observatory oafide bona e se per eerhcenters. research nti ril we article this In . 1 otiigavleo 23 of value a ecliptic (obtaining the on of al-Mam¯un’s as- obliquity the built Syria. measured in cen- tronomers was Tadmor 3rd observatory of plains second the the A in BC. Museum tury Alexandrian signifi- the most establishment of the the since was endeavor scientific This cant observatory. and eto fNas di- of the rection The under at built and was Uzbekistan. Mar¯agha Observatory Iran) modern-day Mar¯agha modern-day in at Samarkand, in those Azerbaijan, were (in observatories lamic 1580. by destruction observatory’s that led to regarding stab- superstitions back and Political bing demise. similar a met 1577, to akin was planets magic. the into of delving supersti- motions under- the to the that trying stand that help presumed not populace did tious it the and and vizier caliph, this serious between Apparently, arisen had observa- instruments. conflicts the its of after charge and in 1125 tory vizier in the was of caliph but death the the completed, by nearly destroyed begun and ordered was 1120 observatory It in An there 1005. 1171. in until Cairo lasted in established was Wisdom, ceased. then but caliph, Abassid un- ninth Baghdad the observations. der in new continued of work basis Astronomical the on work, Ptolemy’s updated on but based of planets tables the produced of and motion diameter, was in Earth miles the 6500 that determined 54 year, to per amounted arcsec equinoxes the of precession the iiyddntgetydmns fe h death ac- the whose after observatory diminish greatly first not the until did was perhaps tivity 1304, It 1264, until in least 1316. Completed at active meters. was cov- hill, it 150 a by of 400 top flattened ering the on situated was h w otscesu n xesv Is- extensive and successful most two The in completed Observatory, Istanbul The of Hall the academy, scientific second A . ı lD¯ın al-T ¯ır al o 33 . ¯us¯ı It (1201-1274). ′ ,cnlddthat concluded ), of its founder. While the motivation for the vations. ’s catalogue was most likely construction of the observatory was astrological, based on observations with a zodiacal armil- the prediction of future celestial events needed lary sphere graduated to 15 arc minutes, with to be carried out on the basis of exact physical interpolation to two-tenths of a mark, or 3 arc measurements. A significant number of instru- minutes. The typical positional accuracy in the ments was built, amongst them equinoctial and catalogue is ± 16 arc minutes. solsticial armillary spheres, and a mural quad- Briefly stated, the purpose of observatories rant of radius 4.3 meters. The observatory’s in Islam was the production of astronomical library at one time contained 400,000 volumes. ephemerides of the Sun, Moon, and planets, The principal accomplishment at Mar¯agha was and possibly also the compilation of a cat- the compilation of the Ilkhanic Tables, which alogue. Royal patronage was required. The were tables of motion of the Moon, Sun, and Mar¯agha and Samarkand Observatories were planets. These explained some of the major intended to be permanent institutions. Cen- shortcomings of Ptolemaic astronomy without, turies ago it was realized that astronomical re- however, suggesting heliocentrism. search is necessarily open-ended. Better posi- The most important astronomer of the 15th tional accuracy is always desirable, so new in- century was Ulugh Beg (1394-1449). For struments have to be designed in order for po- most of Ulugh Beg’s life his father was the sitional accuracy to be improved. Instruments ruler of Transoxiana, a region situated between made of metal were found to last longer and the River Oxus (Amur Darya) and the River give more consistent results than instruments Jaxartes (Syr Darya). This provided the son made of stone or wood. In order to be useful, with the opportunity to indulge his passion for observations had to be carried out for specific astronomy. As a young man Ulugh Beg vis- purposes and according to specific methods. ited the remains of the Mar¯agha Observatory, and he endeavored to build an even greater in- stitution in Samarkand. As many as 70 as- 3 China and India tronomers were active there between 1408 and At the very end of the 17th century one Louis 1437. The largest instrument constructed was a Lecomte published his Memoirs and Observa- of radius 40 meters, a fixed instrument tions of a Journey through China. He noted mounted on the north-south meridian which in some detail the vigilant activity carried out could achieve a resolution of several arc sec- by astronomers at the Imperial Observatory onds, a value not to be exceeded until the in- in Beijing: “Five mathematicians spend every vention of the and the micrometer in night on the tower in watching what passes the 17th century. This sextant was primarily overhead; one is gazing towards the zenith, an- used for observations of the Sun. other to the East, a third to the west, the fourth On the basis of new observations, Ulugh turns his eyes southwards, and a fifth north- Beg and his fellow astronomers compiled a cat- wards, that nothing of what happens in the four alogue of the brightest 1000 visible at the corners of the world may escape their diligent latitude of Samarkand. No one since Ptolemy observation.” Such activity had been going on (ca. 150 AD) or perhaps as far back as Hip- for 3000 years. As a result, the Chinese had parchus had made such extensive stellar obser- accumulated records pertaining to many hun-

2 dreds of lunar and solar eclipses, observations ence of the Emperor radiated in all directions, of novae, supernovae, comets, meteor showers, so the hour circles radiated from the pole, “like aurorae, naked eye sunspots, and even a possi- the spars of an umbrella.” The Chinese laid ble observation of Jupiter’s moon Ganymede in out a system of 28 lunar mansions (xiu), which 364 BC, nearly two millenia before the inven- were defined by the points at which these hour tion of the telescope! The first drive was circles intersected the celestial . built by the Chinese in 132 AD; it was powered One of the most important events in the his- by a constant pressure-head of water in a clep- tory of Chinese science was the arrival of the sydra, or water clock. The Chinese astronomer Jesuits in 1600, towards the end of the Ming Y¨uXi independently discovered the precession Dynasty (1368-1644). They had a very spe- of the equinoxes in 320 AD, finding a value of cific motivation. By demonstrating the supe- about 72 arc seconds per year, two times the riority of Western science, they hoped to con- value found by . Sunspot records vince the Chinese of the superiority of Western in the Chinese annals demonstrate the 11-year religion. Western science clearly won out over solar cycle. the traditional Chinese and Muslim methods Just as spices were transported along the of predicting the solar eclipses of 15 December caravan routes, so too was astronomical knowl- 1610 and 21 June 1629. In November of 1629 a edge. Astronomers from Persia arrived in new calendar bureau was established under the China in 719 AD. The astronomical ties be- direction of the Chinese Christian convert Xu tween the mid-East and far East became quite Guangqi, who supervised the work of fifty as- extensive during the Y¨uan Dynasty (1271- tronomers, many of whom converted to Chris- 1368). In 1267, only eight years after the found- tianity. However, in 1664, at the start of the ing of the Mar¯agha observatory, blueprints for Qing Dynasty (1644-1911), politics led to the seven instruments were sent to China. Actual dismissal of the Jesuits and most of the Chi- models may have followed. nese converts from the calendar bureau. Some In 1270 the astronomer Guo Shoujing (1231- of these astronomers were later beheaded. 1316) built the first equatorially mounted in- The Jesuits regained favor in Chinese as- strument. After the Beijing Observatory was tronomy in 1669. From 1673 to 1676 the Beijing re-equipped in 1276 to 1279 under his direction, Observatory was re-equipped with a new set of it was equal in stature to the Mar¯agha Observa- Tychonic instruments, which are still in place tory. The Chinese also operated an observatory today. However, the astronomical activities in at Nanjing. China were hindered by several factors: 1) the The Chinese did not appreciate or under- interests of the Chinese were limited to calen- stand the Greek geometrical models of plan- drical revision; 2) for Catholics, such as the etary motions or the Arabic use of geometry, Jesuits, the Church’s prohibition against dis- particularly spherical trigonometry and stere- cussing heliocentrism was in effect from 1616 to ographic projection. However, three hundred 1757; 3) the popularity of Tycho’s hybrid geo- years before Tycho Brahe became convinced heliocentric model of the solar system in the that right ascension and declination were the minds of the Jesuits further eclipsed interest in “coordinates of the future”, the Chinese were Copernicanism; and 4) since the most funda- fully committed to their use. Just as the influ- mental motivation of the Jesuits was religious

3 conversion, not scientific progress, they were the name was built by Bernard Walther (1430- not really interested in and telescopic 1504), a wealthy private citizen of Nuremberg, observations. Meanwhile, back in Europe as- who was at the same time the pupil and pa- tronomers such as Jean Dominique Cassini and tron of Regiomontanus (1436-1476). Together John Flamsteed (see §0.5.1 below) were break- they found that the positions of the planets ing new ground in the realms of planetary and differed to a significant degree from the pre- positional astronomy. dictions of the Alfonsine Tables. Their obser- The most significant observatory construc- vations of the comet of 1472 provided a basis tion in India was carried out under the direc- for the modern study of comets. They printed tion of Jai Singh (1686-1743), a Hindu prince astronomical treatises on a printing press set in the court of a Muslim Mogul emperor. Large up in Walther’s house. One such treatise by instruments of masonry were constructed at Regiomontanus laid out the “method of lunar Delhi, Jaipur, Ujjain, Benares, and Mathura. distances” for determining longitude at sea. A The largest instrument was a sundial 27 meters significant innovation at Walther’s observatory tall. Jai Singh wished to follow in the footsteps was determination of the time of observations of Ulugh Beg. He hoped to minimize observa- by mechanical instead of by astrolabes or tional errors by using the largest instruments armillary spheres. Observations with Walther’s possible and felt that portable brass instru- instruments exhibited an improved accuracy, to ments were not the instruments of choice. Jai ± 10 arcmin. Singh’s star catalogue was an update of Ulugh Wilhelm IV (1532-1592), the Landgrave of Beg’s star catalogue, but apparently with no Hesse-Cassel, began systematic observations in new observations. 4o8′ were simply added to 1561. In 1567 his father, the Landgrave of Ulugh Beg’s ecliptic longitudes to account for Hesse, died, and the landgraviate was divided precession over 288 years. up amongst the four sons. Wilhelm was com- pelled to take over the administration of his province, and had to lay aside his astronomical 4 Early European observa- endeavors. In 1575, however, he was visited by tories Tycho Brahe and was inspired to resume ob- serving. Astronomical observations were carried out in Wilhelm constructed a number of metal in- Moslem Spain at Cordova in the 10th century, struments, amongst them an azimuthal quad- at Toledo in the 11th century, and at Castille rant of radius 0.4 m, a torquetrum, a sextant of in the 13th century under the patronage of the radius 1.3 m, a quadrant of 1.5 m radius, and Christian King Alfonso X. The Toledan astro- armillary spheres (see article on Pre- telescopic nomical tables were translated into Latin in instrumentation). He demonstrated the supe- the 12th century; Copernicus owned a copy of riority of metal instruments over wooden ones. them. The Alfonsine Tables, which form the Wilhelm’s most significant innovation was the first state-sponsored astronomical ephemerides rotating dome; he observed from one built in a published for general use, were reprinted as late tower of his castle. His star catalogue of about as 1641. 400 stars, though far short of the intended num- The first European observatory worthy of ber of stars he had hoped to measure, was one

4 of the first made in Europe. clinations with a resolution of 10 arc sec. Per- The most significant observatory prior to haps because of the success of this very instru- the invention of the telescope was that of Tycho ment, a transition began at this time from po- Brahe (1546-1601). It was situated on the 2000 sitional instruments which could be used near acre island of Hven, in the Danish sound be- the celestial meridian to those which were ex- tween Copenhagen and Elsinore. There Tycho plicitly designed to do so. built , the “castle of the heavens”. An auxiliary observatory, Stjerneborg, was It sat in the middle of a square 300 feet on a built in 1584 one hundred feet to the south of side and enclosed by a wall 22 feet high. The the main building. There were five new instru- castle itself had two main levels and was taller ments, the largest of which was an equatorial than a seven story building. In addition to the armillary made of iron, which was 2.9 m in di- observing rooms and verandahs on the upper ameter and could be used to measure declina- level, it contained a dozen or so bedrooms, a tions with a resolution of 15 arc sec. Each of dining room, library, chemical laboratory, and these five instruments was situated in a subter- even a jail in the basement. Begun in 1576, it ranean crypt. Three were sheltered by folding was completed in 1580. Over the north portal roofs. Two had revolving domes. was an inscription, carved in stone: Nec fasces From observations at Hven Tycho discov- nec opes sola artis sceptra perennant (neither ered four inequalities in the Moon’s motion, wealth nor power, but only knowledge, alone, two in longitude (the “variation” and the an- endures). Uraniborg was the first scientific re- nual equation with a period of one solar year), search institute in Renaissance Europe, and Ty- and two in latitude. His observations of Mars cho was the first full-time scientist. were used later by Kepler to discover the ellip- At Uraniborg Tycho and his assistants used tical nature of planetary . From observa- a dozen instruments. The one that produced tions of 1588 to 1591, he produced a catalogue the most accurate stellar positions was a mu- of 777 stars with an improvement in positional ral quadrant of radius 2 m, which was located accuracy of an order of magnitude. More than in the southwest room on the ground floor. A one of Tycho’s instruments produced positional mural quadrant, of course, is attached to a wall, accuracies for his nine principal reference stars fixed on the celestial meridian. Being a quad- of ± 0.6 arc min. The average uncertainty of rant located at latitude 55o54′26′′, it could not the (other) brighter stars in Tycho’s catalogue be used to observe stars north of δ = 55.9 is 1.9 arc min in ecliptic longitude and 1.2 arc degrees. Its fine construction and the use of min in ecliptic latitude. For the fainter stars the transversals1 allowed the determination of de- uncertainties amount to 2.8 and 2.6 arc min, re- 1Transversal dot lines in graduations were first in- spectively. troduced by Richard Cantzlar in 1552 or 1553. This Tycho was able to afford such a magnificent was a variant of the zigzag line system introduced by observatory because his annual income from Johann Hommel (1518-1562), from whom Tycho Brahe various fiefdoms was the equivalent of one per- obtained it. The adoption of concentric circles ruled cent of the Danish government’s income. This with different integral numbers of lines was suggested by P. Nu˜nez in 1542, which led to P. Vernier’s invention continued for a period of nearly 30 years. Such in 1631. The micrometer and filar micrometer were in- only came into more general use in England, France, vented by William Gascoigne about 1640, though they and Holland in the 1670’s.

5 funding in today’s currency would support an 5 The rise of national ob- observatory more expensive than the Hubble servatories and ESO’s Very Large Tele- scope combined. It was not just money, of 5.1 First era: 1576-1725 course, that led to the improvement in instru- mentation. More than one of Tycho’s metal We may distinguish three eras of construction instruments required the workmanship of five of national observatories. Tycho’s island ob- or six people and three years. servatory was, in effect, a national observatory, Tycho’s fortunes, both literally and figura- but the (established 1667) tively, began to decline in 1588 after the death was the prototype of the national observato- of Tycho’s patron, the Danish king Frederick ries that followed. Astronomers in Paris, along II. Tycho left Hven in 1597 and his observatory with those at Royal Greenwich Observatory rapidly fell into decline. (RGO, 1675), Berlin (1701), and St. Peters- Johannes Hevelius (1611-1687), the son of burg (1725), were dedicated to practical mat- a prosperous brewer of Danzig (Gdansk), built ters of national importance: improving naviga- what was for a short time the world’s leading tion (especially the determination longitude at observatory. He copied a number of Tycho’s sea), geodesy, calendar reform, producing accu- instruments, constructing many quadrants and rate stellar coordinates, and the determination sextants of wood or copper. For observing the of ephemerides of the Sun, Moon, and plan- moon and planets he constructed refractors up ets. The establishment of scientific academies to 150 feet in focal length, in which the ob- such as the Accademia dei Lincei (Rome, 1603), jective was mounted on a tall mast. However, the Royal Society (London, 1662), and the for stellar positions he clearly preferred the un- Acad´emie des Sciences (Paris, 1666) testified to aided eye, as he explicitly stated in his Machina the importance and prestige of scientific work. Coelestis (1673). This precipitated a contro- The Paris and Greenwich observatories versy with Robert Hooke, who was a strong stand out as institutional models upon which advocate of telescopic sights. Edmund Halley many subsequent observatories were based. was compelled to visit Danzig in 1679 to try Paris was a reflection of the splendor of the to resolve the controversy. For two months court of Louis XIV, and many significant as- Halley observed with a telescope fitted with tronomers were associated with it. Jean Do- sights while Hevelius used naked eye instru- minique Cassini (1625-1712), his son, grandson, ments. Their observations were of equal accu- and great-grandson, all of whom were unoffi- racy, slightly less than one arc minute. The cial directors at Paris, comprised a most no- Selenographia (1647) of Hevelius was a mile- table astronomy dynasty. The first Cassini dis- stone in lunar mapping. His posthumous star covered four moons of Saturn and the division catalogue (1690) contains the positions of 1564 of the ring system named after him. Paris as- stars. tronomers used extremely long focal length re- fractors (up to 136 feet), mounted on tall masts, to observe the planets and Moon. Ole R¨omer demonstrated the finite nature of the speed of light from observations of Jupiter’s Galilean

6 moons. Paris astronomers carried out the first 5.2 Second era: 1820-1918 geodetic stuveys, covering the full arc of merid- The second era of national observatory build- ian of France by 1700. They later sent expe- ing was characterized by offshoots from previ- ditions to Peru and Lappland. After Nicolas ous national observatories (Royal Observatory de Lacaille went to South Africa in 1751 to Cape, South Africa, 1820), by newer observa- measure the positions of bright stars and to do tories of younger nations (United States Naval further geodetic work, it was proven that the Observatory, 1839), and the rise of astrophys- Earth’s figure was oblate. ical observatories (Potsdam, Prussia, 1874). From the outset both Paris and Green- Other national observatories of the second era wich were mandated to aid navigation through include Pulkovo (Russia, 1839), the Chilean the production of accurate star catalogs, National Observatory (1852), the Argentine ephemerides of the Sun, Moon, and planets, National Observatory (1870), the Smithsonian and the production of nautical almanacs. The Astrophysical Observatory (USA, 1891), and French Connaissance de Temps first appeared Canada’s Dominion Observatory (1903) and in 1679. In 1795 its production became the Dominion Astrophysical Observatory (1918). responsibility of the newly created Bureau des Of nineteenth century observatories, Longitudes, which supervised the work of the Pulkovo deserves special mention. Just as Ty- Paris Observatory. In England the Board of cho was given carte blanche by his sovereign to Longitude supervised the work of the RGO build the finest observatory in the world, so too from 1714 to 1828. By then, with the exis- was Wilhelm Struve (1793-1864) amply funded tence of accurate star positions, ephemerides, by Tsar Nicholas I. Struve ordered an Ertel and the invention of the marine chronometer, transit instrument (for the determination of ab- the problem of determining one’s geographical solute right ascensions), an Ertel vertical cir- position at sea was essentially solved. cle (for the determination of absolute declina- The buildings, staff size, and funding level tions), a Repsold (for the deter- of the RGO were, until the twentieth century, mination of differential stellar coordinates) and modest compared to Paris. The Astronomers prime vertical transit (for the determination of Royal Flamsteed, Halley, Bradley, and espe- aberration and nutation), a Merz & Mahler he- cially George Biddell Airy (1801-1892) were liometer (for the determination of angular sizes amongst the most important astronomers of or angular separations), and the 15-inch Merz their day. Airy organized the observatory as an & Mahler refractor (for the discovery and mea- astronomical factory with himself as factory di- surement of double stars). This refractor was rector and sought to carry out the observatory’s the largest telescope in the world at that time. mission (data acquisition, reduction, and publi- A twin was built for Harvard College Observa- cation of results) as accurately and efficiently as tory in 1847. possible. Today’s service observing and remote The instruments listed above testify to the observing operations are direct descendants of maturation of positional astronomy as a field such efforts. of endeavor. Not only did Pulkovo astronomers measure some of the first stellar parallaxes and discover many double stars, they also produced the most accurate values for the constants of

7 precession, aberration, and nutation – values ments, universities, and research foundations. not superceded until 1964. In the late eighteenth century and through- It is also important to mention that out the nineteenth century various (usually progress in astronomy depended very greatly wealthy) individuals established their own pri- on progress in instrument making and op- vate observatories. tics. Thomas Tompion, George Graham, John The most accomplished private astronomer Bird, Jesse Ramsden, Joseph Fraunhofer, Ed- of all time was the German-English astronomer ward Troughton, Carl Zeiss, Alvan Clark, Al- William Herschel (1738-1822). He pioneered van Graham Clark, Howard Grubb, and George the production of larger and larger reflecting Ritchey are some of the men who made signifi- telescopes (up to 48 inches in diameter), whose cant contributions during this era. light gathering power enabled him to estab- lish the field of galactic astronomy. He carried 5.3 Third era: 1956-present out deeper and deeper surveys of the northern sky, discovered hundreds of binary stars and The present era of national observatory build- many hundreds of nebulae. His “star gauges” ing is characterized by national or international showed that our solar system is situated in a consortia, large budgets, and the investigation large flattened disk of stars. From proper mo- of celestial objects at all electromagnetic wave- tion data he showed that our solar system is lengths. From ground-based observatories we moving toward the constellation Hercules. He may investigate optical, , , and proved that gravity works in the stellar realms submillimeter waves. Because of absorption by by demonstrating that members of a binary star in the Earth’s atmosphere of cer- pair can be observed to revolve about their cen- tain infrared and submillimeter waves, we must ter of mass. He laid the groundwork for studies make some observations from balloons and air- of the evolution of stars and stellar systems. craft. , X-ray, and gamma-ray as- After Herschel’s discovery of the planet tronomy must be carried out from satellites. Uranus in 1781 he was able to give up his first Significant national observatories of the profession (music) and moved to Slough (near third era include the National Radio Astron- Windsor), where his only occasional duty was omy Observatory (USA, 1956), Kitt Peak Na- to give private star parties for members of Roy- tional Observatory (USA, 1957), NRAO (Aus- alty. Herschel’s son John followed in his father’s tralia, 1959), Cerro-Tololo Inter-American Ob- footsteps and took an 18-inch, 20 foot focal servatory (, 1963), European Southern length, reflector to South Africa in the 1830’s, Observatory (Chile, 1964), Anglo-Australian where he conducted a southern sky survey, all Observatory (1967), the Kuiper Airborne Ob- done by eye and telescope, of course. The nebu- servatory (USA, 1975-1995), and the Space lae discovered by the Herschels formed the basis Telescope Science Institute (1981). of Dreyer’s New General Catalogue (1888). Following Herschel’s discovery of Uranus, the German astronomer Johann Hieronymus 6 Private observatories Schr¨oter (1745-1816) quit his post in Hanover and moved to the small town of Lilienthal to Not all significant astronomical work is carried devote himself to . He out at observatories funded by federal govern-

8 built what was then the largest observatory on established a private solar observatory in his the European continent, and was assisted by parents’ backyard in Kenwood, then a suburb Karl Ludwig Harding (who discovered the third of Chicago. This later became part of the Uni- asteroid Juno in 1804) and Friedrich Wilhelm versity of Chicago. Hale became the greatest Bessel. Schr¨oter was also closely associated observatory entrepreneur of all time, establish- with H. W. M. Olbers. Schr¨oter made detailed ing the (1897) and the Mt. drawings of features on the lunar surface and Wilson Observatory (1904). He was the driv- believed he detected changes in the structure ing force behind the establishment of Palomar of some of those features. He inspired many Observatory (1948). observers to dedicate themselves to planetary At the end of the twentieth century, due studies. to advances in electronics and imaging devices, William Parsons, the Third Earl of Rosse many amateurs obtain significant hard data for (1800-1867) built a six foot diameter reflect- professional research projects. Photoelectric ing telescope in Parsonstown, Ireland, which and CCD photometry by amateurs has been revealed the spiral nature of some nebulae (i.e. very important for variable star research and galaxies). has even led to the discovery of a new class of William Huggins (1824-1910) and his wife pulsating stars. Astrometry from CCD imagery Margaret Lindsay Murray established a private routinely provides data on recently discovered observatory at Tulse Hill, near London, where asteroids, which allows the calculation of their they observed the spectra of stars and other ce- orbits. Until very recently the most successful lestial objects. They proved that some nebulae discoverer of supernovae in other galaxies was are star clusters, and were the first to prove that the Australian amateur Robert Evans. others are composed entirely of glowing gas. In 1868, simultaneously with the French- man Jules Janssen, the English amateur Nor- 7 Mountaintop observato- man Lockyer (1836-1920) used a spectroscope ries and the modern era attached to a refractor to observe solar promi- nences outside of a total solar eclipse. He As a result of his optical researches, Isaac New- was subsequently appointed head of the So- ton realized that the Earth’s atmosphere acts lar Physics Observatory at South Kensington. as a lens of sorts and that one could achieve When he retired in 1911 he established his own much better astronomical image clarity by sit- observatory at Salcombe Regis. ing one’s telescope on “some lofty mountain”. The American Henry Draper (1837-1882) In 1741 the French astronomer Fran¸cois de was a pioneer of astrophotography. His widow Plantade carried out the first mountaintop as- funded significant spectroscopic research car- tronomical observations at Sencours Pass, at ried out by astronomers at the Harvard College the foot of Pic du Midi in the French Pyrenees, Observatory. at an of 2300 meters. Unfortunately, George Ellery Hale (1868-1938), the son of he succumbed to altitude sickness and died. a wealthy Chicago industrialist, invented the The next small step leading to improved spectroheliograph while an undergraduate at observing was taken with the establishment in the Massachusetts Institute of Technology. He 1783 of the , an institute

9 of Trinity College, Dublin. The observatory Keck telescopes (each 10-m), the Japanese op- was intentionally sited outside the city (8 km). tical and infrared telescope Subaru (8.3-m), the Also, it had the first fully functional rotating northern Gemini telescope (8.1- m), and the hemispherical dome, and the primary telescope Smithsonian Astrophysical Observatory Sub- was mounted on a pier which was structurally millimeter Array. (and therefore vibrationally) isolated from the Presently, the highest established telescopes walls of the building. are the twin 0.7-m reflectors of the Meyer- In 1856 the Scottish astronomer Charles Pi- Womble Observatory at Mt. Evans, Colorado azzi Smyth spent nearly four months at Tener- (elevation 4313 m). A still higher observatory ife in the and demonstrated is being built at 5000 m about 40 km east that mountaintop observing was both desirable of San Pedro de Atacama in Chile. This is (for image clarity) and viable (for humans). the centimeter -wavelength Cosmic Background The first mountaintop observatory intended Imager, which will investigate the small rip- to be permanent was , which ples in the 3 K background radiation leftover was completed in 1888. Situated at the 1280 m from the Big Bang. This observatory will have summit of Mt. Hamilton, near San Jose, Cali- an oxygen-enhanced environment for the oper- fornia, it boasted a 36-inch refractor by Alvan ators. Clark, then the world’s largest. After the spec- At the time of the publication of this ar- tacular success of the Mt. Wilson Observatory ticle there will be more than 90 optical or in- and the , it became clear frared telescopes in operation around the world that the best seeing was obtained at mountain- with diameters of 1.5 meters or larger (see top sites within 50 miles of the ocean. Be- figure). This includes the now single-mirror cause of the proximity of the ocean, one gets 6.5-m MMT at Mt. Hopkins, Arizona, the a smooth, laminar flow of air over the coastal twin 6.5-m reflectors of the Magellan Project mountains when the prevailing wind conditions (situated at Las Campanas, Chile), the twin are in effect. This has been borne out by the es- 8.1-m Gemini telescopes (one at Mauna Kea, tablishment of many other observatories during , the other at Cerro Pachon, Chile), the the second half of the twentieth century. four 8.2-m elements of the European Southern The highest major observatory in the world Observatory’s (at Cerro (at 4205 m) is at Mauna Kea on the is- Paranal, Chile), Japan’s 8.3-m Subaru Tele- land of Hawaii. From a very modest start in scope (at Mauna Kea), the two 8.4-m elements 1964, Mauna Kea’s astronomical installations of the Large Binocular Telescope (at Mt. Gra- expanded greatly and now include the Univer- ham, Arizona), the two 10-m Keck telescopes at sity of Hawaii 2.2-m telescope, the Canada- Mauna Kea, and the 11-m Hobby-Eberly spec- France-Hawaii Telescope (3.6-m), the NASA troscopic telescope at Mt. Locke, Texas. In Infrared Telescope Facility (3.0-m), the United fact, by the turn of the 21st century more than Kingdom Infrared Telescope (3.8-m), the James half the area of telescopes larger than 1.0 me- Clerk Maxwell submillimeter telescope (15-m), ters will be in telescopes larger than 8 meters. the Caltech Submillimeter Observatory (10.4- Given the expense of such facilities (mea- m), one of the nine elements of the Very Long sured in units of hundreds of millions of dol- Baseline Array (25-m ), the two lars), one might naturally ask why so many

10 large telescopes are being built. It is a reflec- (Amendment list no. 1 25 207-218 (1994)) tion of the blossoming of extragalactic observa- Krisciunas K 1988 Astronomical Centers of the tional astronomy, the desire to give hard data World (Cambridge: CUP) to cosmologists for testing their models, and the desire to discover and study intrinsically faint M¨uller P 1992 Sternwarten in Bildern: Ar- objects such as asteroids in the outer solar sys- chitektur und Geschichte der Sternwarten von tem, brown dwarf stars, and extrasolar planets. den Anf¨angen bis ca. 1950 (Berlin: Springer The design and construction of these state- Verlag) of-the-art telescopes has required the develop- Needham J and Ling W 1959, Science and civil- ment of computer- controlled mirror mounts, isation in China. Volume 3: Mathematics and better ventilated domes (to eliminate as much the sciences of the heavens and the Earth (Cam- as possible the degradation of the seeing due bridge: CUP), pp. 171-461 to air in the dome), thin mirrors (as in the Sayili A 1981 The Observatory in Islam (New case of most of the telescopes mentioned above) York: Arno Press) or multi-mirror systems (36 hexagonal seg- ments in the case of each of the Keck tele- Thoren V E 1990 The Lord of Uraniborg: a bi- scopes, 91 segments in the case of the Hobby- ography of Tycho Brahe (Cambridge: CUP) Eberly Telescope). Modern instrumentation of- Supplementary references: ten uses techniques borrowed from spy satel- lites to achieve diffraction-limited performance. Deane, Thatcher E. 1989, The Chinese Impe- Whereas photographic plates a century ago had rial Astronomical Bureau: Form and Function a quantum efficiency (QE) of less than one per- of the Ming Dynasty Qintianjian from 1365 to cent and photomultiplier tubes typically had 1627, Univ. Washington Dissertation peak QE’s of a few percent, modern instrumen- Dreyer, J. L. E. 1890, Tycho Brahe: a pic- tation can achieve QE’s of 70 percent. Such ture of scientific life and work in the sixteenth instruments, fed by the large objectives of the century, Edinburgh: Adam and Charles Black present generation of telescopes, are producing (reprinted 1977 by Peter Smith, Gloucester, many spectacular results. Furthermore, mod- Mass.) ern computing capabilities are allowing digital Hartner, W. 1950, “The astronomical instru- celestial surveys which would have been techni- ments of Cha-ma-lu-ting, their identification, cally impossible only a few years ago. and their relations to the instruments of the observatory of Mar¯agha”, Isis 41, 184-194 Dick S J 1990 and the national observatory movement: an historical Hermann, Dieter B. 1984, The History of As- overview In: Lieske, J H, Abalakin, V K (eds.) tronomy from Herschel to Hertzsprung, Cam- Inertial coordinate system on the sky (Dor- bridge Univ. Press drecht, Boston, and London: Kluwer), 29-38 Ho Peng Yoke 1997, “Astronomy in China”, in Howse D 1986 The Greenwich list of observa- Encyclopedia of the History of Science, Tech- tories: a world list of astronomical observato- nology, and Medicine in Non-Western Cultures, ries, instruments and clocks, 1670-1850 Jour- Helaine Selin, ed. (Dordrecht: Kluwer), 108- nal for the 17 i-iv, 1-100 111

11 Huang, Yi-Long 1997, “” Fig. 3 - Cerro Tololo Inter-American Obser- in History of Astronomy: an encyclopedia, J. vatory illuminated by moonlight. The largest Lankford, ed. (New York and London: Gar- dome houses the 4-m reflector. (Photo by land), pp. 145-149 Kevin Krisciunas) Kaye, G. R. 1973, The Astronomical Observa- Fig. 4- The number of optical and infrared tories of Jai Singh, Indological Book House, telescopes with primary objectives larger than reprint of 1918 edition a given size, ca. 2001. We include all tele- Krisciunas, K. 1990, “Pulkovo Observatory’s scopes with diameter D greater than or equal status in 19th century positional astronomy”, to 1.5 meters. We count the two 8.4-m diame- in Inertial Coordinate System on the Sky, J. ter elements of the Large Binocular Telescope, H. Lieske & V. K. Abalakin, eds. (Dordrecht: the four 8.2-m diameter elements of the Very Kluwer), pp. 15-24 Large Telescope, and the two 6.5-m telescopes of the Magellan Project as separate instru- Krisciunas, K. 1992, “The legacy of Ulugh ments. Each of the 10-m Keck Telescopes con- Beg”, in Central Asian Monuments, Hasan B. tains 36 hexagonal mirror segments, while the Paksoy, ed. (Istanbul: Isis Press), pp. 95-103 11-m Hobby-Eberly Telescope has 91 hexagonal Krisciunas, K. 1993, “A more complete analysis segments. (Diagram by Kevin Krisciunas) of the errors in Ulugh Beg’s star catalogue”, J. Hist. Astron. 24, 269-280 Pedersen, O. 1976, “Some early European ob- servatories”, Vistas in Astronomy 20, 17-28 Sivin, N. 1973, “Copernicus in China”, in Colloquia Copernicana, II (Wroclaw: Polskiej Akademii Nauk), pp. 63-114 KEVIN KRISCIUNAS

8 Figure captions

Fig. 1 - Pulkovo Observatory, originally com- pleted in 1839, was completely destroyed dur- ing World War II. It was rebuilt by 1954. This is the main building as it appeared in 1989. (Photo by Kevin Krisciunas) Fig. 2 - Lick Observatory, ca. 1936. The large white dome houses the 36-inch refractor, still the second largest in the world.

12