Regiomontanus (rēˌjēōmŏnˌtāˈnəs) [key] [Lat., = belonging to the royal mountain, i.e., to Königsberg], 1436–76, German astronomer and mathematician, b. Königsberg. His original name was Johannes Müller. In 1461 he went to Rome with Cardinal Bessarion and learned Greek in order to translate Greek writings. In 1468 he was called to the court of the king of Hungary to make a collection of Greek manuscripts, and three years later he settled at Nuremberg, where, with his pupil and patron, Bernhard Walther, he established an observatory and a printing press. Among other works they published the Ephemerides for the years 1474–1506, calculated by Regiomontanus, and Georg von Purbach's Theoricae planetarum novae. Summoned by Pope Sixtus IV, Regiomontanus went to Rome in 1475 to assist in reforming the calendar and was made bishop of Regensburg. He died in Rome. He made improved instruments, both mathematical and astronomical, introduced algebra into Germany, and did much to further trigonometry.