ASTRONOMICAL OBSERVATORIES. - I. HISTORICAL NOTES. - Leaving aside the very ancient Chinese astronomical observatories, about which our information is quite uncertain, it is known that in the classical world the first observatories appeared in Mesopotamia, perhaps around the 10th century B.C., and consisted of tall, multi-storied pyramidal towers (the ziggurats of the Babylonians), some remains of which have been found at Horsabad, near Nineveh. As is well known, the Chaldean priests (whom V. Schiaparelli rightly called the great fathers of astronomy) were most diligent students of the stars and of celestial motions; indeed, they had succeeded in discovering a practical method (the so-called Saros period) for the approximate prediction of solar and lunar eclipses.
From Chaldea, astronomy passed into Egypt and thence into Greece; and, after the Macedonian conquest, the center of studies shifted from Athens to Alexandria in Egypt, flourishing under the reign of the Ptolemies, who founded there the famous museum, with a very rich library and a celebrated astronomical observatory illustrated by Eratosthenes (276-196 B.C.), one of the greatest astronomers of antiquity. The Alexandrian astronomical school came to a close, so to speak, with Claudius Ptolemy (2nd century A.D.), who in his Almagest summarized the knowledge of past generations.
With him the ancient era of astronomy ends and the astronomical Middle Ages begin. In the Middle Ages astronomy was much cultivated by the Arabs, who translated the Almagest into their language (later translated into Latin by Gerard of Cremona, in 1180) and carried out many observations of planets and comets with their astrolabes and triquetra. A precious Arab astrolabe, built at Valencia in 1175 by Sa'id Ibrāhīm, is preserved in the astronomical museum of the Observatory of Rome on the Monte Mario.
In particular, among Arab astronomical observatories, those deserving mention are that of the astronomer al-Battānī (Albatenius) in Mesopotamia (10th century), and that of Ulugh Beg at Samarkand (Turkestan); the works of al-Battānī, rediscovered in the Library of the Escorial, were recently published by A. Nallino in the Arabic text with a Latin translation.
With the birth of the modern age, true astronomical observatories are seen to arise in Europe as well. Among the first, prior to the invention of the telescope, is that of Kassel (Germany), erected in 1561 by William IV, Landgrave of Hesse, and the celebrated one of Tycho Brahe on the island of Hven (Baltic Sea), where the great Danish astronomer carried out those methodical and exact observations of the positions of the planet Mars, which later led Kepler to the discovery of the famous three laws on the heliocentric motion of the planets. But a true flowering of astronomy takes place only after the invention of the telescope (1609) and after Galileo's first discoveries concerning the spots of the Sun, the mountains of the Moon, the phases of Venus, the satellites of Jupiter, the Milky Way, etc.
The following century therefore marks the founding of the great European observatories: Paris (1667), Greenwich (1675); Berlin (1705); St. Petersburg (1725); Vienna (1735), etc.
As regards Italy in particular, mention is made at Rome of the Observatory of S. Maria in Vallicella, founded by the Ponteo who carried out there observations of the comet of 1680: observations that had the honor of being mentioned by Newton himself. This is the first Italian observatory of which there is record, since the earlier observations of Clavius, of Scheiner and of E. Divini had been carried out on terraces with portable telescopes; and it is followed by the observatory of the University of Bologna founded in 1714. A few years later the Jesuits, who resided in the Palazzo di Brera in Milan, where they held courses in philosophy and theology, founded the Milanese observatory (1760), calling to direct it the illustrious mathematician and astronomer Fr. Ruggero Boscovich. Shortly afterwards (1766), by decree of the Venetian Senate, the Observatory of Padua was erected in the tower of Ezzellino; then Fr. De Caesaris founded at Rome (1780), near S. Maria Maggiore, the Caetani Observatory, later transferred to the Capitoline Hill, while a few years later (1787) the abbot Giuseppe Calandrelli founded the Observatory of the Collegio Romano in a small tower he had erected on that building and still visible from the square of the same name.
After the storm of the French Revolution had passed, the abbot Giuseppe Piazzi (who, some years earlier, had founded the Observatory of Palermo on the tower of S. Ninfa and had greatly distinguished it by the discovery of the first minor planet, Ceres Ferdinandea) was invited by Ferdinand I to complete and direct the Observatory of Naples, whose construction had already been begun shortly before at Capodimonte (1812). Later (1823) Pope Leo XII reorganized studies with the brief Quod divina sapientia and established the founding of an observatory on the great eastern tower of the Palazzo del Campidoglio, in Rome; this foundation was entrusted to the abbot Feliciano Scarpellini, who transferred to the Capitoline Hill the material of the old Caetani observatory that he had directed and added new scientific instruments to it. Almost simultaneously, G. Plana founded the Observatory of Turin on one of the towers of Palazzo Madama; D. De Vecchi brought into being the Observatory of Florence in the Palazzo del Museo delle scienze, etc. The end of the 19th century saw the rise (1888) of the Vatican Observatory, then located on the Leonine tower in the Vatican walls.
II. MODERN ASTRONOMICAL OBSERVATORIES
With the dawn of the 20th century, astronomical observatories completely abandoned the old towers in which they had always lived and instead required the possession of a plot of land (preferably on a hill) where they could place, in separate pavilions, the instruments intended for measuring the positions of planets and stars (transit instruments; meridian circles, etc.). In fact, the great accuracy that is demanded today in positional measurements requires that these instruments have the greatest possible stability and therefore be placed directly on the ground upon very solid foundations. Moreover, the increasingly widespread use of celestial photography, especially in astrophysics for the study of nebulae, stellar spectra, etc., often advises carrying out such photographs under particular conditions, for example, in the mountains. On the other hand, the photographic plates thus obtained must then be measured and studied with the utmost care; and practice has shown that for every hour spent photographing the sky, fifty or seventy hours at the desk are then required for examining the plates. But nothing forces this long examination to be carried out in the same place where the photographs were taken; and furthermore, the great observatories often have rich libraries, perform time-signal services, etc., and are also seats of advanced courses for students, so that it would be harmful to remove them far from the city and from the great universities. The problem has therefore been solved by providing modern observatories with suitable "branch observatories."
Thus, for example, as regards Italy, the astronomical observatory of Rome has abandoned its ancient urban sites and has moved to the summit of Monte Mario on the first meridian of Italy, placing the positional instruments in the park in separate pavilions, and has recently erected a branch station of its own on the Gran Sasso d'Italia at an altitude of 2300 m above sea level. Similarly, the observatory of Bologna has erected a branch at Loiano in the Apennines; that of Padua at Asiago at an altitude of 1000 m; that of Milan at Merate, etc. And likewise the observatory of Turin was moved by its director, G. Boccardi, from the towers of Palazzo Madama to a suitable park near Pino Torinese; the observatory of Florence, through the efforts of G. B. Donati, passed from the old Palazzo del Museo to the hill of Arcetri near the city. And lastly, even the Vatican Observatory, under the direction of the Jesuit Father J. Stein, has left the old Leonine Tower for the pontifical park of Castel Gandolfo.
But the great advances of astronomy have also led to a specialization of astronomical observatories. At present it is inconceivable that a single observatory could concern itself with all the fields of astronomy, just as no institute today could profitably concern itself with all the fields of medicine. Modern observatories therefore tend to be subdivided into astronomical observatories properly so called, whose tasks concern especially positional astronomy, or classical astronomy; into astrophysical observatories, which deal predominantly with the physical constitution of celestial bodies; into solar observatories, which study the sun; and finally into astronomical laboratories, which devote themselves particularly to calculations and to the examination of photographic plates obtained at other observatories.
Naturally, purely geodetic observatories are left aside (in Italy the observatory of Carloforte, which deals with the movements of the Earth's pole), as well as meteorological or seismic ones, which observe meteorological phenomena, earthquakes, microseisms, etc., noting that such a division is not, nor can it be, absolute, but only indicative. Thus, for example, there are observatories that are at once astronomical and solar, or astrophysical and solar, astronomical and meteorological, astronomical and seismic, etc.
At present the United States undoubtedly constitutes the nation in which astronomy is most cultivated, both because of the great number and because of the high potential of the observatories at its disposal. It will suffice to recall those of Mount Palomar, Mount Wilson, Mount Hamilton, as well as the Lowell Observatory, etc.
III. ASTRONOMICAL INSTRUMENTS
The principal instruments of observatories are: the high-precision clock, the meridian telescope, the equatorial telescope (visual or photographic), the astrograph, the reflector and the solar tower; the first concern more especially astronomical observatories, the last astrophysical and solar ones.
The clocks are generally placed in basements, or in rooms at constant temperature; and often also under pneumatic bells at constant pressure. The meridian telescopes, placed in separate pavilions in the park or garden of the observatory, are of modest dimensions, and can move only in the plane of the meridian and are therefore suited to identifying the precise instant at which a celestial body passes the meridian, as well as the altitude it reaches at that moment above the horizon; from these observations the astronomer derives the celestial coordinates of the body examined (right ascension and declination), the correction of the clock, the longitude and the latitude of the observatory. Equatorials are large telescopes (the largest, which belongs to the Yerkes Observatory, has a lens more than one metre in diameter) placed under rotating domes; they serve for the study of double stars, of variable stars, for the search for stellar parallaxes, for the examination of the physical peculiarities of the planets, etc., and for this purpose they have a special mounting (called equatorial) and are driven by an electric motor that allows them to follow a celestial body in the sky automatically, in its apparent motion, from rising to setting. Astrographs are photographic equatorials, of modest dimensions, but provided with a system of lenses that allows them to photograph a wide region of the sky; they are very useful especially for the search for and the determination of the positions of minor planets and comets. Reflectors are large equatorials in which the objective lens is replaced by a parabolic mirror (or spherical, in the modern Schmidt type); since the mirror concentrates at the same focus all the light rays whatever their wavelength, and since it can also be built of very great dimensions (that of Mount Palomar has a diameter of 5 m.), the reflector can be considered as the principal instrument of astrophysics for the study of stellar spectra, for the photography of very distant nebulae, etc. The solar tower is a tall tower (that of Mount Wilson is about 50 m. high; that of Monte Mario, in Rome, which is the largest Italian one, about 35 m.) which supports, in its interior, a vertical telescope of a length equal to the height of the tower. At the summit of the tower, under a rotating dome, there is a system of movable mirrors (coelostat), which causes the sun's rays to fall upon the objective lens of the telescope.
The astronomer places himself in a room on the ground floor of the tower, where a large focal image of the sun is formed, which he can study or photograph comfortably. In the basement there is another apparatus (spectroheliograph), which allows the spectroscopic study of the individual regions of the sun, as well as the taking of photographs using only the light emitted by certain chemical elements, hydrogen, calcium, etc. This makes it possible to identify the distribution and the movements of the clouds of calcium, hydrogen, etc. in the upper layers (chromosphere) of the Sun.
For brevity, mention will here be made of the accessory astronomical instruments (micrometers, photometers, chronographs, spectrographs, plate-measuring machines, calculating machines, etc.), as well as of the meteorological and seismic instruments (barometers, thermometers, hygrometers, anemometers, seismometers, etc.), recalling at the same time that some observatories also possess rich libraries and at times (as, for example, the Observatory of Rome) even an astronomical museum. - See plate XXVIII.
Bibliography
Giuseppe Armellini
IV. SCIENTIFIC OBSERVATORIES IN THE MISSIONS
Scientific observatories in the missions attract the esteem and goodwill of peoples toward the Church and also serve to combat widespread popular superstitions. The most celebrated observatory in the history of the missions is the one that was erected at the court of Peking at the beginning of the 17th century by the Jesuits, among whom were distinguished Fr. Johann Adam Schall von Bell, a German, who built the observatory itself, and Fr. Ferdinand Verbiest, a Fleming, who was its first European director. The scientific work of these fathers at the court indirectly brought great advantages to the missions (v. CINA, III. Evangelizzazione). The suppression of the Society of Jesus at the end of the 1700s put an end to the scientific work of the Jesuits at the court of Peking, nor was it ever resumed afterward.
Instead, in the 2nd half of the last century other scientific observatories arose.
In Manila, a meteorological station was founded by the Jesuits in 1865, which, under the direction of Fr. Federico Faura y Prat, a Spaniard, soon developed into the Observatory of Manila. Although the Fathers' first concern was the forecasting of typhoons, the geomagnetic, seismological and astronomical sections were soon added to the meteorological section. It was, however, completely destroyed in February 1945, at the time of the evacuation of the city by the Japanese army. Fr. Faura made a great name for himself with the invention of an instrument for forecasting typhoons.
The Observatory of Zi-ka-wei near Shanghai, which in a certain sense marks the revival of the ancient imperial Observatory of China, was founded by the French Jesuits in 1873. Fr. Louis Froc, called the "Father of typhoons," and his successor, Fr. Ernest Gherzi, rendered great services to the economic and commercial development of that Chinese coast through their increasingly exact and reliable forecasts of typhoons. From the scientific point of view, however, no less important was the work of the other sections established in the Observatory of Zi-ka-wei and in its branch at Zo-sè. The Observatory published for meteorology a Bulletin de prévision de temps (daily) and for astronomy: Annales de l'Observation de Zo-sè. Among the most recent and important publications of Fr. E. Gherzi, one may note: La météorologie de la Chine (published by the Pontifical Academy of Sciences [Rome 1939]) and Climatological atlas of Asia (Shanghai
1944). In 1950, the buildings were occupied by the communist government of China.
Of lesser importance is the Observatory of Ambohidempona on the island of Madagascar, founded in 1889 by the French Jesuits. For some time, in collaboration with government institutions, the Fathers occupied themselves with the study of cyclones, which are fairly rare in that region. But the most important work of that observatory consists of the geomagnetic research carried out by its present director, Fr. Charles Poisson. It nevertheless also has sections for astronomy, seismology and meteorology. It also had an important geodesy section.
In 1907 the French Jesuit Fr. Bonaventure Berloty founded the observatory of Ksara in Lebanon, which is part of the University of St. Joseph in Beirut. From 1911 until 1944 the official direction of the State Meteorological Service was joined to that observatory. Besides the meteorological section it comprises the astronomical, geomagnetic and seismological sections. The climatological study of Lebanon constitutes its most important work. Until 1940 the Observatory published: Annales de l'Observatoire de Ksara, and until 1945: Climatologie aéronautique. Now there are published there monthly: Bulletin mensuel de climatologie and Bulletin sismologique prévisoire.
Fr. Edward Pigot, an Irish Jesuit, was in 1908 the founder of a seismological station, which developed into the astronomical and seismological Observatory of Riverview, near Sydney in Australia. The present director is Fr. Daniel O'Connell. The main work of that observatory consists of photographic photometry, especially of variable stars.
Since in the mission countries governments always wish to have their own observatories, it is foreseen that the observatories in the missions will gradually lose their public importance and will rather be transformed into institutes of scientific research affiliated with universities or colleges directed by missionaries.
Alfonso Smeters