Abd-al-Rahman Al Sufi

(Picture possibly shows Al Sufi or a contemporary "idealized" person)


Abd al-Rahman Al Sufi, known in the West as Azophi, was one of the most outstanding practical astronomers of the Middle Ages. He lived at the court of the Emire Adud ad-Daula in Isfahan (Persia), working on astronomical studies based on Greek work, especially the Almagest of Ptolemy. In 964 Al Sufi published his famous book "Kitab al-Kawatib al-Thabit al-Musawwar" ("Book of Fixed Stars"), a masterpiece on stellar astronomy. It is considered important even now for the study of proper motions and long period variables.

In his descriptions and pictures of Andromeda, he included "A Little Cloud" which is apparently the Andromeda Galaxy M 31. He mentions it as lying before the mouth of a Big Fish, an Arabic constellation. This cloud (marked "A" on the picture) was apparently commonly known to the Isfahan astronomers, very probably before 905 AD. The nebula was re-discovered with a telescope by Simon Marius on 15 Dec. 1612.

D N NI Y I T Observer Name Con Type S Author Title
1 N 224 964? E v Marius 15.12.1612 M 31, Andromeda Nebula AND Sb 1 Al-Sufi Book of Fixed Stars 

Al Sufi contributed several corrections to Ptolemy's star list, in particular he did own brightness/magnitude estimates which frequently deviated from those in Ptolemy's work. Also, he was the first to attempt to relate the Greek with the traditional arabic star names and constellations, which was difficult as these constellations were completely unrelated and overlapped in a complicated way. In this book, he probably also cataloged the Omicron Velorum cluster IC 2391 as a "nebulous star", and an additional "nebulous object" in Vulpecula, a cluster now known as Brocchi's Cluster (Collinder 399). He named the southern group of stars al-Baqar al-Abyad or the "White Bull" after receiving reports from Arab navigators in the Malay Archipelago. This group of stars could be identical to the "Nubecula Major" (Large Magellanic Cloud).