Abū Saʿīd Sījzī and his al-Jāmiʿ al-Shāhī

All that we know about the life and times of al-Sijzī, the 10th century Iranian Muslim mathematician and astronomer, is limited to the small pieces of information provided by other authors’ accounts and some of his own works. On the basis of al-Sijzī’s mathematical works and the extant maunscripts written in his hand, some modern scholars have estimated his date of birth in about 942 ad. Numerous works of al-Sijzī are extant in three areas: mathematics, astronomy and astrology. Although there is a considerable number of astrological compositions among al-Sijzī’s works, little research has been done about them. One of the most important astrological works of al-Sijzī is al-Jāmiʿal-Shāhī, in which the author mentions some historical and astronomical events of the 10th century. Nevertheless, there exist some other collections of al-Sijzī’s astrological works catalogued under the title “al-Jāmiʿ al-Shāhī” and often mistakenly considered as the same book as al-Jāmiʿ al-Shāhī. In this article we try to provide more accurate information about al-Sijzī’s life and period of activity and to show that these astrological collections are not a single work and are different from al-Jāmiʿ al-Shāhī.