Ulugh Beg Observatory, Samarkand

Timeline

1. c. 1420–1429Samarkand · UzbekistanUlugh Beg built an observatory on high ground north of Samarkand, inviting scholars such as Qadi Zada al-Rumi to direct it, and constructed a curved mural quadrant with a radius of about 40 meters for precise measurement of celestial altitudes using enormous graduations.
2. c. 1437–1449Samarkand Observatory · UzbekistanAfter long-term direct observation, the team completed the Zij-i Sultani, containing coordinates of over a thousand stars; its precession value is remarkably close to modern measurements, and the catalog circulated and was cited in the Islamic world and Europe for a long time.
3. 1449–1647Samarkand · UzbekistanAfter Ulugh Beg was murdered, the observatory lost court support and observations ceased; in the 17th century the quadrant's wall was destroyed, while the underground foundation and curved trench survive to this day, and after 20th-century archaeological excavation it was opened as a museum.