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The Vatican Observatory (Specola Vaticana) is the astronomical research and educational institution of the Holy See. The headquarters of the observatory are located at Castel Gandolfo, Italy, sharing the summer residence of the Pope. The dependent Vatican Observatory Research Group is hosted in the Steward Observatory at the University of Arizona. Its current director is José Gabriel Funes of the Society of Jesus.

The Observatory operates a 1.8 metre telescope atop Mount Graham near Safford, Arizona, USA, which together with its associated research facility is known as VATT (Vatican Advanced Technology Telescope), whose mirror was the first one constructed at the Steward Observatory Mirror Lab.

In early 2008, it was announced that the Castel Gandolfo observatory was to be moved, in order to provide more room for the Pope to receive diplomats at his summer residence. The observatory will be moved to a former convent a mile away from the castle.

The Vatican Observatory now bears the official title, “Specola Astronomica Vaticana.” To understand its history it is necessary to remark that the designations osservatorio or specola are not restricted to astronomy, but may mean any elevated locality from which aerial phenomena are observed. From this point of view the history of the Specola Vaticana has passed through four successive stages.

(1) The first period of the Vatican Observatory is thus described in the Motu Proprio of 1891 by Leo XIII:

Gregory XIII ordered a tower to be erected in a convenient part of the Vatican buildings, and to be fitted out with the greatest and best instruments of the time. There he held the meetings of the learned men to whom the reform of the calendar had been entrusted. The tower stands to this day, a witness to the munificence of its author. It contains a meridian line by Ignazio Danti of Perugia, with a round marble plate in the centre adorned with scientific designs. When touched by the rays of the sun that are allowed to enter from above, the designs demonstrate the error of the old reckoning and the correctness of the reform.

The first half of this narration is based upon a tradition supported by Gilii and Calandrelli (see LILIUS); it is connected with the Vatican Observatory, at least as far as the locality is concerned. The tower is 73 metres above sea level and stands over the museum and library, between the courtyards Belvedere and della Pigna. It is often called the “Tower of the Winds”

(2) The second period of the Vatican Observatory deals mainly with the person of Mgr. Filippo Luigi Gilii, whose life has been written by Lais. Gilii was born in Corneto in 1756, and died in Rome, in 1821, a beneficed clergyman of St. Peter’s Basilica. He was a universal genius, well versed in physics and in biology, in archeology and in the Hebrew language . The Gregorian Tower was then in charge of the Vatican librarian, to which office Cardinal Zelada had been appointed in 1780. Zelada wished to honour the traditions of the tower by devoting its upper part to an observatory. In 1797 he obtained the sanction of Pius VI, and placed over the entrance to the tower the Latin inscription Specula Vaticana. The upper story was fitted up with meteorological and magnetic instruments, with a seismograph, a Dolland telescope, a small transit and pendulum clock, and the observatory was given in charge of Mgr. Gilii. From 1800 to 1821 Gilii made an uninterrupted series of meteorological observations, reading the instruments twice a day (after 6 a. m. and 2 p, m.), according to the programme of the Mannheim Meteorological Society. The observations of about seven years of the long series are published, while the rest are in great part preserved as manuscripts in the Vatican Library. There are also deposited astronomical observations of eclipses, comets, Jupiter’s satellites, and of a transit of Mercury. Gilii’s scientific activity extended beyond the Vatican Observatory and beyond Rome. The meridian line in front of St. Peter’s, with the obelisk as gnomon and the readings of the seasons by the length of the shadow, is due to him; so are also the signs on the floor of St. Peter’s Basilica, indicating the lengths of the greatest churches of the world, likewise the two old clocks of French and Italian style, in the front of the basilica, and finally the first lightning rod on St. Peter’s cupola.

Similar memories of him exist in various churches and cities of Italy. The tombstone in Ara Co li calls him a man “mitissimi ingenii, modestiæ singularis, pius.” At the death of Gilii the Vatican Observatory was discontinued, for the following reason: Pius VII and Leo XII raised the standard of studies in the papal states. The latter pope, in his Apostolic letter, “Quod divina sapientia,” gave instructions about observatories, publications, and intercourse with foreign scientists. In 1787 the observatory at the Roman College had been founded, under Calandrelli, and was declared preferable to the Vatican, as more accessible to students in the city, and not obstructed by the great cupola of St. Peter’s (Giornale Arcadico, II, p. 407). On the advice of Father Boscovich the instruments were then transferred from the Gregorian Tower to the Roman College.

(3) The revival of the Vatican Observatory in its third period was occasioned, on the one hand, by the loss to the Church of the Roman College and its observatory in 1870, and on the other, by the exposition of instruments presented to Leo XIII by the Italian clergy for the celebration of his golden jubilee of priesthood, in 1888. The Barnabite Father Denza, well-known as founder of the Italian Meteorological Society, then proposed to Leo XIII to preserve the instruments in the Gregorian Tower, and to restore that locality to its former purposes. The plan was accepted and a series of the best instruments was procured, partly from donations by Hicks in London, partly by purchase of self-registering apparatus from Richard in Paris. From the observatory of the late Marquis of Montecuccoli in Modena, of which Denza had been director, a four-inch equatorial, a three-inch transit instrument, and four pendulum clocks with two chronometers, were acquired. Father Denza had still broader plans.

The year before in 1887, Mouchez had organized the cooperation of a number of observatories for continuing Argelander’s observations to fainter magnitudes by means of photography. At the second meeting of the committee in Paris, in 1889, Denza declared his intention to join in the work. For this purpose, Leo XIII ceded to the Vatican Observatory a second tower, more than 400 metres distant from the Gregorian. It is the western of the two towers remaining from the Leonine Fortress, which had been built for defence against the Saracens in 848-53. With a diameter of 17 metres and a thickness of 4.5 metres in the lower walls, it seemed large and strong enough to support the thirteen-inch photographic refractor which was ordered from Gauthier in Paris.

During the four years following, the observatory remained in charge of the vice-director, Father Lais, of the Oratory who has conducted the photographic work from the beginning, all at his own expense. From 1898 until 1905 the directorship was in the hands of the Augustinian Father Rodriguez, a specialist in meteorology. Seven volumes were published during the third period of the observatory, four under Denza, the fifth under Lais, and the last two under Rodriguez.

(4) The fourth and present period of the Vatican Observatory began with the appointment in November, 1904, by Pius X of Archbishop (now Cardinal) Maffi as President of the Specola. His first step was to remedy the great difficulty caused by the separation of the two towers. According to his plans, the Gregorian Tower was to be abandoned to historical archives, and the second round tower of the old Leonine Fortress, with the adjoining summer residence of Leo XIII, was to be given over to astronomy. The two old towers were to be connected with each other by a passage over the fortification wall, with an iron bridge spanning a gap of 85 metres in length.

For carrying out these plans, the author of the present article was designated in the audience given to Cardinal Maffi on 14 March, 1906, and officially appointed on 26 April. The fortification wall, a thousand years old, which extends about 400 metres, is now crowned with four rotary domes, covering the astrographic refractor in the Leonine Tower, and a new sixteen-inch visual telescope in the second tower, called Torre Pio X. A four-inch equatorial stands on a half round bastion, at the west end of the bridge, and a photoheliograph at the east end of the old wall, over the barracks of the gendarmes.

The old transit instrument is mounted on a vault over the main walls of the new residence. After the material restoration of the observatory, the main problems were a library and the measuring of the astrographic plates. The rich meteorological library was consigned to the Pontifical Academy Lincei, and the old meteorological and seismic instruments were mainly sent to the observatory in Valle di Pompei, An astronomical library is now filling two rooms of the new residence; old treasures were secured to it by the loan of the scientific collection from the Vatican Library, the latter confining itself to historical and literary branches. The astrographic plates are being measured with two new Repsold machines, which are placed in a neighbouring convent, in charge of three Sisters. For nearly four years the director enjoyed the cooperation of Father Stein, S.J., by which it was possible to publish the first three numbers of the new series, besides minor essays, and the last two series of the atlas of variable stars. At the reunion of the Astrographic Congress at Paris in 1909, P. Lais presented thirty charts reproduced by himself on silver-bromide paper.

Vatican Advanced Technology Telescope

The Vatican Advanced Technology Telescope (VATT) truly lives up to its name. Its heart is a 1.8-m f/1.0 honeycombed construction, borosilicate primary mirror. This was manufactured at the University of Arizona Mirror Laboratory, and it pioneered both the spin-casting techniques and the stressed-lap polishing techniques of that Laboratory which are being used for telescope mirrors up to 8.4-m in diameter. The primary mirror is so deeply-dished that the focus of the telescope is only as far above the mirror as the mirror is wide, thus allowing a structure that is about three times as compact as the previous generation of telescope designs.

The 0.38-m f/0.9 Zerodur concave secondary mirror was manufacted by the Space Optics Research Laboratory (Chelmsford, MA). Its mount allows control of its focus and positioning to 0.1 microns, an accuracy needed for such a fast optical system.

The telescope mount is of altitude-azimuth design and was manufactured by L&F Industries (Huntington Park, CA). It features direct drive motors on the two axes, leading to a very compact and rigid mount. The compactness allows a telescope that is very stable in a high wind and easily repositioned on the sky. It also means that a small dome can be used and so the distortions in an image produced by air surrounding a telescope can be minimized.

The building in which the telescope is housed is designed to isolate thermally the ambient temperature in the dome from the heated observing room and living quarters. This isolation is achieved by using the section between the dome and the main facility as a thermal barrier and by exhausting air from this section and from the dome out from the north and mainly downwind side of the building.

Tours of Mount Graham International Observatory, including the VATT, are run on Saturdays from mid-May to mid-November (weather-permitting) from Discovery Park out of Safford.

Science and Theology

While the whole nature of the Vatican Observatory is to be a bridge between science and the Catholic Church, studies involving science, philosophy, and theology have formed an explicit part of the Observatory’s activity since 1987 when it organized two interdisciplinary conferences as a response to Pope John Paul II’s request for something both to commemorate Sir Isaac Newton’s epoch-making book, Philosophia Naturalis Principia Mathematica, and to contribute to the dialogue between the two cultures. The first meeting to commemorate the Newton tercentenary was held in Cracow, May 1987, and resulted in the book, Newton and the New Direction in Science. This prepared for the second meeting, September 1987, at Castel Gandolfo, whose proceedings and a message from Pope John Paul II are given in Physics, Philosophy, and Theology: A Common Quest for Understanding.

These beginnings led the Observatory, together with the Center for Theology and the Natural Sciences of Berkeley, California, to initiate a series of five, interdisciplinary research workshops with the theme of ‘Divine Action in the World’. These were by invitation only for the workshop process to be effective. The workshops in the series have each resulted in a book: Quantum Cosmology and the Laws of Nature, Chaos and Complexity, Evolutionary and Molecular Biology, Neuroscience and the Person, Quantum Physics.


1. THE VATICAN OBSERVATORY: IN THE SERVICE OF NINE POPES, S. Maffeo (2001), trans. G.V. Coyne, 429 pp., $25.00, €20.00 ISBN 88-209-7242-5