Ulugh Beg Completes the Zij-i Sultani

Ulugh Beg completed the Zij-i Sultani in Samarkand in 1437. It is a star catalogue that gives positions of almost a thousand stars, based on new observations. Ulugh Beg was a Timurid prince and an astronomer, and he ran a large observatory in Samarkand. The catalogue was among the most accurate star lists of its time and was used by later astronomers.