concerning the planetary order from their works, and show how they responded 'Ur's impact on the reformation of Ptolemaic astronomy, and finally, I will elucidate Shrz's way of incorporating 'Ur's achievement into the hay'a tradition standardized by s's Tadhkira f 'ilm al-hay'. Abhar's astronomical worksTehran, Majlis shura Library MS 6195 (= MS B) contains an astronomical work entitled Book of the Summary and Abridgment of the Almagest (Kitb talkh al-majis wa-tahdhb-hu; henceforth the Talkh) in 155 folios.As far as we know, the Talkh is transmitted at least by two other manuscripts, that is, Tehran, Milli Library MS 20371 and Istanbul, Ayasofya MS 2583m. 4Unfortunately, the information of who was the author is missing in all the three manuscripts, but, as Mara Jos Parra Prez rightly identifies, 5 its author was almost undoubtedly Athr al-Dn al-Abhar (d.1262 or 1265).Abhar was especially known as an author of philosophical works, but he wrote quite a few works on mathematics and astronomy, 6 and his name was registered in the list of the Margha associates. 7He was also known as a famous teacher of philosophy, having many disciples, one of whom was Najm al-Dn 'Al ibn 'Umar al-Qazwn al-Ktib (d.1277), the author of ikmat al-'ayn, 8 whose name was also contained in the list of the Margha associate. 9We must note that the name of Ktib was mentioned in the introduction of the Talkh, whose beginning is as follows: 10Q1 Since I have been associated with the most notable and closest one of my companions with my kindness towards him for a while, that is, 'Al ibn 'Umar ibn 'Al al-Qazwn -may God give him success because of the fortunes-, who is like a child of mine, studying exact sciences and philosophical canons, and he has prepared for leading his study to the investigation of the art of the Almagest, then I want to write for him a summary of books by the Ancients covering the secrets of it = the art of the Almagest in more plain description and arrangement.Thus, I composed this book containing parts of this art as well as its preparatory topics necessary for it besides the principles of the Element (MS B, f. 2b).This introduction shows that Abhar aims to summarize the Almagest for Ktib.Here, we must note that in Book 10, Section 1 "How to divide the heaven into orbs", he explains the planetary order with recourse to occultations and parallaxes, as follows:Q2 Since the Moon occults Mercury and Mercury occults Venus, it is known that Mercury's orb is above the Moon's orb and under Venus's orb.And it is found that the Sun's parallax is smaller than Venus' parallax, while it is not found that Mars has any parallax, so it is known that the Sun's orb is above Venus's orb and under Mars' orb.And it is found that Mars occults Jupiter, and Jupiter occults Saturn, which occults the fixed stars, so it is known that Jupiter's orb is above Mars' orb and under Saturn's orb and Saturn's orb is under the orb of the fixed stars (MS B, f. 114a). 11
Taro Mimura (Sat,) studied this question.