The Vatican Observatory has operated continuously since 1774, when the Papacy established the Observatory of the Roman College in Rome. The Church's interest in astronomy predates that: the Gregorian Calendar, issued in 1582 by Pope Gregory XIII, required precise astronomical data to calculate the date of Easter. The original Rome dome was eventually closed because St. Peter's blocked the view. A later facility moved to Castel Gandolfo, 25 kilometers southeast of Rome, when Rome's light pollution made observation impossible. Today the Vatican also operates a 1.8-meter telescope on Mount Graham, Arizona.
In the early 20th century, Father John Hagen recruited a team of nuns to help build a photographic star atlas. Sisters Emilia Ponzoni, Regina Colombo, Concetta Finardi, and Luigia Panceri "helped map and catalog nearly half a million stars" as part of an international celestial mapping project.
The Observatory currently employs Jesuit astronomers and researchers from multiple countries, and publishes peer-reviewed research in astrophysics.
