The Imperial Astronomy of Petrus Apianus (1495-1552) is one of the most impressive and beautiful scientific works of all time. Dedicated to Charles V, who had appointed Apian as his court astronomer, it explains the use of the astrolabe (for calculating the altitude of stars) and other instruments used for computing planetary positions, data that was crucial to be able to navigate the oceans. In the true humanist spirit, Apian was not only a cartographer and an astronomer, he also had a printshop and sold scientific instruments. Apian’s works are famous for their use of volvelles, paper constructions with rotating parts. These analog “computers” allowed for complicated tables to be presented in a visually attractive way, making the book into a two-dimensional scientific instrument.