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The Church has had a long-standing interest in astronomy due to the astronomical basis of the calendar by which holy days and Easter are determined. For instance, the Gregorian Calendar, promulgated in 1582 by Pope Gregory XIII, was developed by Aloysius Lilius and later modified by Christoph Clavius at the Collegio Romano from astronomical data. 
On September 29, 1935, Pope Pius XI officially inaugurated the new headquarters of the Specola Vaticana (Vatican Observatory) at Castel Gandolfo. With new telescopes, a new astrophysical laboratory for spectrochemical analysis, and a young staff comprising Jesuit scientists, this inauguration marked the beginning of an intense period of scientific achievements at the Observatory.
The Vatican Observatory is an astronomical research and educational institution supported by the Holy See. In 1993 the Observatory, in collaboration with Steward Observatory, completed the construction of the Vatican Advanced Technology Telescope on Mt. Graham, Arizona, probably the best astronomical site in the Continental United States. 
The Vatican Observatory works with the Vatican Observatory Foundation to promote education and public engagement in astronomy, and constructive dialogue in the area of faith and science.
It supports a dozen priests and brothers (Jesuits and diocesan) from four continents who study the universe utilizing modern scientific methods.

The 80th anniversary of the Vatican Observatory, Castel Gandolfo is marked by two stamps. The €0,80 value featuring Pope Pius XI, the observatory building, and the Schmidt telescope installed in 1935. The €0,95 value depicts Pope Francis and the refractor telescope also installed in 1935. Both stamps incorporate stars into the design because research into variable stars is an area of study by Jesuit astronomers at the observatory. The stamps were printed in sheets of 10.

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