Ulugh Beg (Chaghatay/Persian: (میرزا محمد طارق بن شاهرخ (الغ‌بیگ Mīrzā Muhammad Tāriq ibn Shāhrukh (Ulugh Beg) - also Uluğ Bey, Ulugh Bek and Ulug Bek) (c. 1393 or 1394 in Sultaniyeh (Persia) – October 27, 1449) was a Timurid ruler as well as an astronomer, mathematician and sultan. His commonly-known name is not truly a personal name, but rather a moniker, which can be loosely translated as "Great Ruler" or "Patriarch Ruler" and was the Turkic equivalent of Timur's Perso-Arabic title Amīr-e Kabīr. His real name was Mīrzā Mohammad Tāregh bin Shāhrokh. Ulugh Beg was also notable for his work in astronomy-related mathematics, such as trigonometry and spherical geometry. He built the great observatory in Samarkand between 1424 and 1429.