Encyclopædia Britannica, Ninth Edition/Ulugh Beg, Mirza Mohammed Ben Shah Rok

ULUGH BEG, Mirza Mohammed Ben Shah Rok (1394-1449), astronomer, grandson of Timur (q.v.), succeeded his father as prince of Samarkand in 1447, after having for years taken part in the government, and was murdered in 1449 by his eldest son. He occupied himself with astronomical pursuits, and erected an observatory at Samarkand, from which were issued tables of the sun, moon, and planets, with an interesting introduction, which throws much light on the trigonometry and astronomical methods then in use (Prolegomenes des Tables Astronomiques d Ouloug Beg, ed. by Sedillot, Paris, 1847, and trans lated by the same, 1853). The serious errors which he found in the Arabian star catalogues (which were simply copied from Ptolemy, adding the effect of precession to the longitudes) induced him to redetermine the positions of 992 fixed stars, to which he added 27 stars from Al Sufi's catalogue, which were too far south to be observed at Samarkand. This catalogue, the first original one since Ptolemy, was edited by Th. Hyde at Oxford in 1665 (Tabulse Longitudinis et Latitudinis Stellarum Fixarum ex Observatione Ulugbeighi), and in 1843 by Baily in vol. xiii. of the Memoirs of the Royal Astronomical Society.