MÆSTLIN, MICHAEL, in Latin Mæstlinus, a celebrated astronomer of Germany, was born in the duchy of Wittemberg; but spent his youth in Italy, where he made a speech in favour of Copernicus's system, which brought Galileo over from Aristotle and Ptolemy, to whom he had been hitherto entirely devoted. He afterwards returned to Germany, and became professor of mathematics at Tubingen; where, among his other scholars, he taught the great Kepler, who has praised several of his ingenious inventions, in his Astronomia Optica. Though Tycho Brahe did not assent to Mæstlin's opinion, yet he allowed him to be an extraordinary person, deeply skilled in the science of astronomy. Mæstlin published many mathematical and astronomical works; and died in 1590.