Johannes Müller von Königsberg (6 June 1436 – 6 July 1476), better known as Regiomontanus , was a mathematician, astrologer and astronomer of the German Renaissance, active in Vienna, Buda and Nuremberg. His contributions were instrumental in the development of Copernican heliocentrism in the decades following his death. Regiomontanus wrote under the Latinized name of Ioannes de Monteregio (or Monte Regio; Regio Monte); the toponym Regiomontanus was first used by Philipp Melanchthon in 1534. He is named after Königsberg in Lower Franconia, not the larger Königsberg (modern Kaliningrad) in Prussia. Source: Wikipedia (en)