In its historical roots and traditions the Vatican Observatory is one of the oldest astronomical institutes in the world. For the first foreshadowing of the Observatory can be traced to the constitution by Pope Gregory XIII of a committee to study the scientific data and implications involved in the reform of the calendar which occurred in 1582. The committee included Father Christoph Clavius, a Jesuit mathematician from the Roman College, who expounded and explained the reform. From that time and with some degree of continuity the Papacy has manifested an interest in and support for astronomical research. In fact, three early observatories were founded by the Papacy: the Observatory of the Roman College (1774-1878) (illustrated), the Observatory of the Capitol (1827-1870), and the Specula Vaticana (1789-1821) in the Tower of the Winds within the Vatican. These early traditions of the Observatory reached their climax in the mid-nineteenth century with the researches at the Roman College of the famous Jesuit, Father Angelo Secchi, the first to classify stars according to their spectra. With these rich traditions as a basis and in order to counteract the longstanding accusations of a hostility of the Church towards science, Pope Leo XIII in 1891 formally re-founded the Specola Vaticana (Vatican Observatory) and located it on a hillside behind the dome of St. Peter's Basilica.

Several religious orders contributed personnel and directors to the Observatory. These included Barnabites, Oratorians, Augustinians, and Jesuits.

For a little more than four decades astronomical research, which included a prominent international program to map the whole sky, was carried out in the shadow of St. Peter's, but it eventually became obvious that the urban growth of the Eternal City was brightening the sky to such an extent that the fainter stars could no longer be studied.

Thus it was that Pope Pius XI provided a new location for the Observatory at the Papal Summer Residence at Castel Gandolfo in the Alban Hills some 25 kilometers southeast of Rome.

It is here that the modern observatory, entrusted to the Jesuits, was refounded in the 1930s with the construction of two new telescopes, the installation of an astrophysical laboratory for spectro-chemical analysis, and the expansion of several important research programs on variable stars. With the installation of a Schmidt wide-angle telescope in 1957 research was extended to other topics such as new techniques for the classification of stars according to their spectra. This is still an active program at the observatory and recalls the pioneering work of Angelo Secchi.

Details of these historical telescopes can be found on the Instrumentation page of this web site.

With the continuously increasing population of Rome the skies above the Observatory again became too bright. For this reason in 1981, for the first time in its history, the Observatory founded a second research center, the Vatican Observatory Research Group (VORG), in Tucson, Arizona in the United States, one of the world's largest and most modern centers for observational astronomy. The Observatory staff have offices at Steward Observatory of the University of Arizona (picture shows S.O. on the right and its Mirror Laboratory under the football stadium at the end of the road). From here they have access to all of the modern telescopes located in the Tucson area.

In 1993 the Observatory, in collaboration with Steward Observatory, completed the construction of the Vatican Advanced Technology Telescope ( VATT ) on Mt. Graham, Arizona, probably the best astronomical site in the Continental United States. This is the first optical-infrared telescope of the Mount Graham International Observatory (MGIO), a project which in the coming years will see the construction of some of the world's most sophisticated and largest telescopes.

The VATT has pioneered the new technology of creating large, lightweight, stable mirrors in a rotating furnace (see picture to right). With the VATT we are pursuing long-term research programs which, although they were the hallmark of research at Castel Gandolfo, we have never been able to carry out before in Tucson. Thus from its two centers, located at Castel Gandolfo and at Tucson, the Observatory is continuing various current studies and international collaborations.

As translated by Dr. Martin McCarthy, S.J., the dedication plaque of the VATT reads: 
w tower for studying the stars has been erected during the XV year of the reign of John Paul II on this peaceful site so fit for such studies, and it has been equipped with a new large mirror for detecting the faintest glimmers of light from distant objects. May whoever searches here night and day the far reaches of space use it joyfully with the help of God.

The library at Castel Gandolfo contains more than 22,000 volumes and possesses a valuable collection of rare antique books including works of Copernicus, Galileo, Newton, Kepler, Brahe, Clavius, and Secchi. In addition there is a unique meteorite collection from which a knowledge of the early history of the solar system is being derived. Research results are published in international journals. The Annual Report is distributed to more than 400 institutes around the world.

The observatory also publishes the Studi Galileiani, a series of current research on Galileo and the Copernican controversies.

At intervals of about every two years we host either at Castel Gandolfo or at Tucson a scientific meeting with some twenty invited scholars on one of the current studies of the Observatory.

Summer Schools in Astronomy and Astrophysics are now a biannual event in the Vatican Observatory's programs.