The first epoch-making astronomer who was brought into intimate relations with the Pope of whom we have definite knowledge was Regiomontanus. He is deservedly known as the Father of Modern Astronomy for his initiation of series of calculations and publications with regard to the heavens and his establishment at Nuremburg of a regular observatory. He was summoned to Rome to direct the calculations for the correction of the calendar, but unfortunately died there at the early age of forty. His invitation to Rome for this purpose came within the same decade when, if we were to trust certain modern historians of the relations of the Popes to science, Pope Calixtus III issued his supposed bull against Halley’s comet. The bull has never been found. The attitude of the Popes towards science is much better illustrated by the invitation to Regiomontanus and the encouragement of astronomical research thus afforded than by the fictitious bull against the comet. The supposed bull has, however, played a large role in convincing a number of people of Church opposition to science, some of them being professors of science who knew nothing about the almost simultaneous appointment of Regiomontanus as Papal Astronomer.
James J. Walsh, The Popes and Science (1908)