It’s 1540 and you’d like to cast a horoscope. If you are the Holy Roman Emperor Charles V, you might turn to the
The volume pictured here is held at the
The volume contains 21 moving paper parts. Circular paper “spinners” called volvelles function as “computers” as they are arrayed with astrological information. The user could spin the layers to align the planets and calculate horoscopes or eclipses. A thread attached to the center of each volvelle used to feature small, luxurious seed pearls. This mimicked the function of the astrolabe—typically a hand-held, metal astronomical instrument. Apianus created horoscopes using these methods for Emperor Charles V and his brother Ferdinand I. This was a tribute to his noble patron, one which earned him extra privileges from the emperor.
In the Renaissance, astronomers and astrologers were largely one and the same. An emperor valued the predictive and research endeavors of his astronomers. So, how accurate were the astrological insights of Astronomicum Caesareum? The text is based on a geocentric model of the world—the dominant view before the publication of the works of Copernicus. However, despite this inaccuracy, Apianus accurately identified the paths of five comets including Halley’s Comet. He also was able to predict a future eclipse while describing some historical ones.
To learn more about the making of books such as Astronomicum Caesareum, check out this
The Astronomicum Caesareum is a richly illustrated Renaissance scientific manuscript.
The book features many moving paper models that function like astrolabes.
The author, Petrus Apianus, used these moving diagrams to cast horoscopes and track the heavens.
Only about 40 copies of this early printed work survive.