The one who made Samarkand famous. Ulugh Beg, a Tartar prince and ruler of Turkestan under whose rule the Timurid dynasty reached its cultural summit. He was an exceptional astronomer and mathematician of his time. Ulugh Beg made Samarkand famous as one of the leading cities of and there, in 1424, established a madrasa, a centre of higher learning, where astronomy was taught. In 1428, in the same city he began the construction of a magnificent three-story observatory - more than two hundred fifty feet in diameter and one hundred twenty feet high. He equipped the observatory with the best and most accurate astronomical instruments available then where well-know astronomers and mathematicians worked there. Ulugh Beg published, in 1437, his famous work a new catalogue of stars entitled 'Zidj-i-Djadid Sultani' - a diverse collection of observations and computations, the position of the fixed stars, the course of the stars, and the knowledge of time. An English translation of this work was published in 1917. Ulugh Beg computed the length of the year as 365 days 5 hours 49 minutes and 15 seconds, a fairly accurate value. In addition, he prepared Tables of planetary Motions, which were very popular amongst the astronomical community. He studied the yearly movements of the five bright planets - Saturn, Jupiter, Mars, Venus and Mercury. His compilations of data and of tables of sines and tangent at one-degree intervals, still considered very accurate, are accurate to eight decimal places. Ulugh Beg whose other interests were poetry, history and study of the Qur'an was assassinated in Samarkand and this catastrophe led to the neglect of the observatory and the City slowly phased out as the leading centre of astronomy. Ulugh Beg was born Muhammad Targai Ulugh Beg, the grandson of Tamerlane and son of Timurid king Shah Rukh, at Sultaniyya in Central Asia.