Regiomontanus[rejiohmontaynus], Lat name of Johannes Müller
Mathematician and astronomer, born in Königsberg (Lat Mons Regius, hence his pseudonym), Germany. He studied at Vienna, and in 1471 settled in Nuremberg where a rich patrician, Bernard Walther, offered him an observatory. He established the study of algebra and trigonometry in Germany, and wrote on a variety of applied topics. In 1474 he was summoned to Rome by Sixtus IV to help reform the calendar.