1911 Encyclopædia Britannica/Ulugh Beg
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ULUGH BEG, MIRZA MAHOMMED BEN SHAH ROK (1394-1449), Persian astronomer, son of the shah Rok and grandson of Timur, 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 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 (Prolégomènes des tables astronomiques d'Ouloug Beg, ed. by Sédillot, Paris, 1847, and translated 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 Sûfi'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 (Tabulae longitudinis et latitudinis stellarum fixarum ex observatione Ulugbeighi), by G. Sharpe in 1767, and in 1843 by F. Daily in vol. xiii. of the Memoirs of the Royal Astronomical Society.
See Delambre, Histoire de l'astronomie du moyen âge; Poggendorff, Biographisch-litterarisches.