Sultanic Zij (Zīj-i Sulṭānī)

Timeline

1. 1420–1429Samarkand Observatory · SamarkandUlugh Beg built a large meridian instrument and quadrant observatory at Samarkand, gathering scholars such as al-Kashi and Qāḍīzāde to re-observe stellar positions and precession errors in older zij works like the Ilkhanic Zij. This program formed the observational basis of the Sultanic Zij, rather than being a simple precessional extrapolation of older tables.
2. 1437–1439Samarkand · SamarkandThe table was written in Persian, containing the motions of the Sun, Moon, and five planets, eclipses, and the ecliptic longitude, latitude, and magnitudes of about 1,018 stars. Except for 27 southern stars unobservable from Samarkand, which were taken from al-Sufi's star catalogue with precessional corrections, most positions came from new observations at the observatory, along with new values for the stellar year and the obliquity of the ecliptic.
3. 1449–1600Transoxiana–Istanbul manuscript network · Ottoman EmpireAfter Ulugh Beg's death, scholars such as Qūshjī carried the table to courts beyond Transoxiana. Manuscripts were used, commented upon, and adapted in Persia, the Ottoman Empire, and India, making it one of the most important practical star catalogues of the 15th–16th century Islamic world and partly displacing the Ilkhanic Zij in everyday use.
4. 1665Oxford · OxfordHyde, Sharp, and 19th-century Baily successively published the star catalogue, allowing European scholars to compare the Samarkand observations with the systems of Ptolemy and Tycho. Modern research shows that before Tycho, this 1437 catalogue was among the most accurate large star catalogues in Eurasia, and its manuscripts remain objects of scholarly collation in the history of science.