Mīrzā Muhammad Tāraghay bin Shāhrukh (Chagatay: میرزا محمد طارق بن شاہ رخ, Persian: میرزا محمد تراغای بن شاہ رخ), better known as Ulugh Beg (الغ بیگ) (March 22, 1394 in Sultaniyeh, Persia – October 27, 1449, Samarkand), 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" (compare modern Turkish ulu great, and bey, chief) or "Patriarch Ruler" and was the Turkic equivalent of Timur's Perso-Arabic title Amīr-e Kabīr. His real name was Mīrzā Mohammad Tāraghay bin Shāhrukh. Ulugh Beg was also notable for his work in astronomy-related mathematics, such as trigonometry and spherical geometry. He built the great Ulugh Beg Observatory in Samarkand between 1424 and 1429. It was considered by scholars to have been one of the finest observatories in the Islamic world at the time and the largest in Central Asia. He built the Ulugh Beg Madrasah (1417–1420) in Samarkand and Bukhara, transforming the cities into cultural centers of learning in Central Asia. He was also a mathematician of the 15th century — albeit his mental aptitude was perseverance rather than any unusual endowment of intellect. His observatory is situated in Samarkand which is in Uzbekistan. He ruled Uzbekistan, Tajikistan, Turkmenistan, Kyrgyzstan, southern Kazakhstan and most of Afghanistan from 1411 to 1449.