Zij-i-Sultani

Zij-i-Sultani is a Zij astronomical table and star catalogue that was published by Ulugh Beg in 1437. It was the joint product of the work of a group of astronomers working under the patronage of Ulugh Beg.

Alongside Abd al-Rahman al-Sufi's "Book of Fixed Stars", the "Zij-i-Sultani" is generally considered the greatest of star catalogues between those of Ptolemy and Tycho Brahe. The serious errors which he found in previous star catalogues of Islamic astronomy (many of which had simply updated Ptolemy's work, adding the effect of precession to the longitudes) induced him to redetermine the positions of 992 fixed stars, to which he added 27 stars from Abd al-Rahman al-Sufi's catalogue "Book of Fixed Stars" from 964, which were too far south for observation from Samarkand. This catalogue, one of the most original of the Middle Ages, was edited by Thomas Hyde at Oxford in 1665 under the title "Tabulae longitudinis et latitudinis stellarum fixarum ex observatione Ulugbeighi" by G. Sharpe in 1767, and in 1843 by Francis Baily in vol. xiii. of the "Memoirs of the Royal Astronomical Society".

In 1437 Ulugh Beg determined the length of the sidereal year as 365.2570370...^d = 365^d 6^h 10^m 8^s (an error +58^s). In his measurements within many years he used a 50 m high gnomon. This value was improved by 28^s 88 years later in 1525 by Nicolaus Copernicus (1473-1543), who appealed to the estimation of Thabit ibn Qurra (826-901), which was accurate to +2^s.

See also

* Zij

References

* E. S. Kennedy, "A Survey of Islamic Astronomical Tables", Transactions of the American Philosophical Society, (1956) 46(2), pp. 3-4, 44-5.
* 1839. L. P. E. A. Sedillot (1808-1875). Tables astronomiques d’Oloug Beg, commentees et publiees avec le texte en regard, TomeI, 1 fascicule, Paris. A very rare work, but referenced in the Bibliographie generale de l’astronomie jusqu’en 1880, by J.
* 1847. L. P. E. A. Sedillot (1808-1875). Prolegomenes des Tables astronomiques d’Oloug Beg, publiees avec Notes et Variantes, et precedes d’une Introduction. Paris: F. Didot.
* 1853. L. P. E. A. Sedillot (1808-1875). Prolegomenes des Tables astronomiques d’Oloug Beg, traduction et commentaire. Paris.