Ulugh Beg Compiles Zij-i Sultani Star Catalog

In 1437, Ulugh Beg and his team of astronomers at the Samarkand observatory completed the Zij-i Sultani (Royal Tables), an astronomical catalog containing the positions of 1,018 stars. Unlike predecessors who updated Ptolemy's measurements, Ulugh Beg conducted new observations using instruments including a 40-meter sextant built partially underground. The catalog's accuracy remained unmatched until Tycho Brahe's work in the late 16th century. The work included measurements of celestial positions, planetary motions, and Earth's axial tilt. The Zij-i Sultani spread throughout the Islamic world and later reached Europe.