The Three Story Sextant and the Zij-i Sultani

This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.

The Ulugh Beg Observatory was built in the 1420s near Samarkand by the Timurid ruler and astronomer Ulugh Beg, grandson of the conqueror Timur. Its centerpiece was a three story sextant, a giant curved track cut partly into a hillside, an engineering approach distinct from the smaller portable instruments most observatories of the period relied on, built at that scale specifically to improve the precision of the astronomical measurements Ulugh Beg's scholars were taking.

The observatory's astronomers produced the Zij-i Sultani, a star catalogue and set of astronomical tables accurate enough to be referenced in European astronomy for centuries afterward, making it the last major observatory of the classical Islamic astronomical tradition before its instruments and scholarship were dispersed following Ulugh Beg's own assassination in 1449. The observatory's working life therefore closed with the death of the ruler who had built and directed it, its scientific legacy surviving in the tables his scholars had produced long after the institution itself had ceased to function, a pattern of an institution's science outliving its founder that Ulugh Beg's observatory shares with several other observatories of the classical Islamic astronomical tradition built under a single patron's direct sponsorship.