REGIOMONTANUS, German astronomer, whose real name was Johann Muller, but who assumed that of 1R.egiomontanus, in allusion to the place of his birth, Konigsberg (Kings Mountain), Fran conk: b. 6 June 1436; d. Rome, 6 July 1476. Having received a classical education at Leip zig, he placed himself under Purbachius von Purbach), the professor of mathe matics at Vienna, and under him became one of the first astronomers of that age. With Purbachius he accompanied Cardinal Bessarion to Rome in 1461, where Beza gave him further instruction in Greek literature, and he now completed a new abridgment in Latin of the of Ptolemy (1496), correcting many errors in the former translation, made by George of Trebizond. In 1471 he built an ob servatory at Nuremberg and established a press, but after three years returned to Rome on the invitation of Sixtus IV, who employed him in the reformation of the calendar and rewarded his services by raising him to the bishopric of Ratisbon (1475). He died, according to some, of the plague, according to others poison administered by the son of George of Trebizond out of revenge for his having exposed the errors of his father. Regiomontanus was the
first in Germany to apply himself to the culti vation of the neglected science of algebra. He made great improvements in trigonometry, into which he introduced the use of tangents. His refutation of a supposed discovery of the quad rature of the circle and numerous writings on various subjects of natural philosophy display extensive learning and great acuteness. His astronomical observations from 1475 to 1506 ((Ephemerides') are very accurate. Among his other works (Kalendarium) (about 1474), (De Reformatione Kalendarii) (1489) • Comet Magnitudine Longitudineque> (1531) ; (De Triangulis Omnimodis> (1533); (Tabula: Directiotmm Prejectionumque in Nativitatibus multum utiles> (1585). Consult Gunther, 'Johannes Muller' (in the (Allgemeine deutsche Biographic,' Vol XXII, 1855) ; also Ziegler, (Regiomontanus als, geistiger Vorliifer des Columbus) (1874).