Printed paper instruments called volvelles provided astronomers with the positions of the Sun, Moon, and planets, freeing them from performing lengthy calculations derived from planetary tables. Bassantin’s work, a general overview of astronomy, partly copies Petrus Apianus’s Astronomicum Cæsareum of 1540. The Irish astronomer William Molyneux (1656-1698) once owned this copy.

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Although the magnetic lodestone had been used since ancient Greek times, Gilbert’s work contains the first experimental research on the properties of magnetism. Gilbert argued, correctly, that the Earth is a natural magnet and that the Earth’s magnetic poles are relatively near its geographic poles. As a result, mariners were better able to use the lodestone as an effective navigational tool.

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Navigators for Columbus would have taken the Alfonsine tables, a set of astronomical tables, on their expeditions to the New World. Once thought to have been devised by astronomers at the court of Alfonso X, the tables were extremely useful to navigators and crucial to early explorers. Because the tables considerably simplified astronomical calculations, the user could determine planetary positions without having to work with the underlying mathematical models that described the Ptolemaic solar system.

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