The Astronomicum Caesareum is a beautifully crafted astrolabe manual, to be used in order to calculate planetary alignment and the location of the stars. Petrus Apianus, a German court astronomer for Emperor Charles V dedicated the work to his patron. In return the emperor promoted Apianus to court mathematician and made him an imperial knight. Seed pearls sewn into the pages, moving pieces, and dozens of drawings and diagrams make the manuscript a masterpiece. Apianus provided new commentary on Halley’s Comet (seen in 1531 and shown in the last image) and called for instruments to be used in astronomy rather than outdated calculation tables. Only 40 known copies remain in the world.