The star catalogue of Wilhelm IV, Landgraf von Hessen-Kassel

Abstract

Near the end of the 16th century Wilhelm IV, Landgraf von Hessen-Kassel, set up an observatory with the main goal to increase the accuracy of stellar positions primarily for use in astrology and for calendar purposes. A new star catalogue was compiled from measurements of altitudes and angles between stars and a print ready version was prepared listing measurements as well as equatorial and ecliptic coordinates of stellar positions. Unfortunately, this catalogue appeared in print not before 1666, long after the dissemination of Brahe’s catalogue. With the data given in the manuscript we are able to analyze the accuracy of measurements and computations. The measurements and the computations are very accurate, thanks to the instrument maker and mathematician Jost Bürgi. The star catalogue is more accurate by a factor two than the later catalogue of Tycho Brahe.