Astronomicum Caesareum

Also known as Petrus Apianus, Peter Apian (1495-1552) was a prominent German humanist, mathematician, astronomer, and cartographer. The author of various works, his Astronomicum Caesareum is considered by many as "perhaps the most beautiful scientific book ever printed" (Brashear, Ronald, Daniel Lewis, and Owen Gingerich. 2001.) Published in 1540, the work predated De revolutionibus orbium coelestium, the groundbreaking treatise on a heliocentric solar system by Nicolaus Copernicus (1473-1543), by only three years. The book was thus scientifically very quickly outdated for the time. Not a few astronomers of the following generations – among them Johannes Kepler (1571-1630) – therefore expressed derision concerning this work. It was not until the 20th century that this last great creation of Ptolemaic astronomy attracted the attention of researchers as well as that of bibliophile collectors.

A True Renaissance Man

Probably born Peter Bienewitz in Leisnig an der Mulde in Saxony as the son of a successful shoemaker, he studied at the universities of Leipzig and Vienna. Since the imperial court had a keen interest in astrology and astronomy, the University of Vienna had long been a center for the study of astronomy as well as geography and mathematics. From Vienna, Apian went to Regensburg and then Landshut in 1523, eventually teaching mathematics at University of Ingolstadt from 1526 until his death in 1552. However, applied mathematics – astronomy and geodesy – were not particularly popular subjects there and mainly medical students attended Apian's lectures on astronomy. Physicians needed basic astronomical knowledge, for example in connection with bloodletting therapy, in order to determine the ideal times for their interventions.

One of the Original Self-Publishers

At the same time, he ran a print shop in Ingolstadt together with his brother Georg. There, in addition to Peter Apian's own works, they mainly printed those of Johann Eck (1486-1543), a fellow professor and most important theological opponent to Martin Luther (1483-1546). By operating the print shop, Apian did not merely want to tap additional sources of income, but above all to make himself independent of outside printers. In order to avoid errors in the printing of their works, which were difficult to typeset, quite a few famous astronomers in the early modern era – such as Tycho Brahe (1546-1601) or Johannes Hevelius (1611-87) – operated their own printing workshops. Apian's first significant astronomical publication was the Instrument Book, printed in 1533, in which he describes scientific instruments that served astronomers, surveyors, and navigators alike.

A Masterpiece of Science and Printing

Printed in 1540, the large-format Astronomicum Caesareum is a magnificent masterpiece of 16th-century book art that took eight years to complete. The number of printed copies is unknown. However, 111 copies have survived to this day, 34 of which are in Germany. The hand coloring was already done in Apian's workshop, which was rather unusual at that time. After the publication of the Astronomicum Caesareum, Apian's print shop largely ceased its work and was sold after his death. Apian dedicated the work to Emperor Charles V (1500-58) and his brother Emperor Ferdinand I (1503-64), who both financed the printing and made the author a rich man. Moreover, the book earned him the title of court mathematician and elevation to the peerage.

Encyclopedia of the Stars

The Astronomicum Caesareum summarizes the state of astronomical knowledge in the mid-16th century. In the foreground of the first part is the representation of the planetary movements and the determination of the position of the celestial bodies, which made the work interesting not least for astrologers. The movements of the celestial bodies are illustrated with the help of 21 rotating discs made of paper, the so-called volvelles. The Astronomicum Caesareum is thus not only a theoretical astronomy book, but at the same time a scientific instrument with which the position of the sun, moon and planets can be determined. Such rotating representations can already be found in Apian’s earlier writings and are part of a tradition going back to the 15th century. In total, the work includes 58 hand-colored woodcuts created by Michael Ostendorfer (1490/94-1559) and Hans Brosamer (1494-1554). The introductory celestial map lists the 1,022 stars known to Apian and the second part of the work deals with astronomical instruments and comets. Apian, by the way, was the first to recognize that the tail of a comet always faces away from the Sun.