# Johannes Regiomontanus, or Johannes Müller

Back to people overviewA mathematician, astrologer and astronomer who made great contributions to the development of the Copernican system. After studying at the University of Vienna he was appointed to the faculty, thereby becoming a colleague of Peurbach, with whom he had studied astronomy. The two men became fast friends and worked closely together as observers of the heavens. Among Regiomontanus' most important achievements was a portable sundial built for Pope Paul II, a pioneering work on arithmetic and algebra, and his 'Epitome of Ptolemy's Almagest'. Copernicus referred to this work as an influence on his own ideas about the solar system.