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.