Ulugh Beg Observatory

Ulugʻbek rasadxonasi

The ruins of an observatory built by Ulugh Beg in the 1420s. Underground lies a giant sextant arc with a radius of 40 metres, and the star catalogue he compiled was two centuries ahead of Europe in accuracy.

Ulugh Beg (1394 to 1449) was a grandson of Timur, ruler of Samarkand, and the greatest astronomer of the 15th century. In the 1420s he built a three-storey circular observatory on a hill northeast of the city. It was 46 metres in diameter. Its core instrument was a giant meridian sextant (the Fakhri sextant) with a radius of about 40 metres. The graduated arc was set into a deep groove that ran from underground up to the roof of the building. It was used to measure the altitude of the sun, moon and planets as they crossed the meridian. Ulugh Beg and his assistants used it to calculate the length of the year to within less than one minute, along with the obliquity of the ecliptic and the positions of 1,018 stars. The results were compiled into the Zij-i-Sultani, whose accuracy Europe did not surpass until the 17th century. In 1449, Ulugh Beg was murdered by his son, and religious leaders later demolished the observatory. It was not until 1908 that Russian archaeologist Vyatkin, guided by written sources, found and excavated the arc segments buried 11 metres underground. These are the only original parts that can be seen today. A small museum built in 1970 beside the site displays copies of the star catalogue, a model of the reconstructed observatory, miniature paintings and a monument to Ulugh Beg. Entry for foreigners is about 40,000 som (about 25 yuan). Opening hours are 09:00 to 18:00. It is about 2 kilometres northeast of Siyob, a 5-minute taxi ride, or a 20-minute walk from the Afrasiyab Museum. Allow about 45 minutes. A guide or the museum exhibits are essential to understand the significance of the arc.

Ulugh Beg Observatory

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