As-Sufi

'ABD AL-RAHMAN AL-SUFI (AZOPHI) (903 - 986 C.E.)

'Abd al-Rahman Al-Sufi, known in the West as Azophi, was one of the two most outstanding practical astronomers of the Middle Ages. Al-Sufi was the first astronomer to describe the 'nebulosity' of the nebula in Andromeda in his book of constellations (atlas of heavens). 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. We now know this group of stars as Nubecula Major (the greater Magellanic Cloud).

Al-Sufi prepared charts of the heavens from his own observations and carefully adjudged their magnitudes. His book 'Kitab al-Kawatib al-Thabit al-Musawwar' was a masterpiece on stellar astronomy. It is available in the original Arabic and in French translation by Schjellerup. Kitab al-Kawatib is considered important even now for the study of proper motions and long period variables. In it he included theta Eridani among the 13 brightest stars then known. Ulugh Beg, the grandson of Timur (Tamerlane), in 1437 found it to be of the first magnitude in his list of fixed stars. Edmond Halley in his voyage to St. Helena at the beginning of the Eighteenth century saw it as a star of the third magnitude.

Al-Sufi stated that the color of the Sirms (alpha canes majoris) does not change, which is confirmed by later observations. Ironically, Seneca reported to have observed it red in Rome, Ptolemy in Alexandria reddish, and Schmidt (1841) in Athens had observed it white after finding yellow for a few days. It is presumed that these contradicting observations must have been due to local variations of weather. Al-Sufi observed the color of Algol, beta Persei, (Arabic Al-Ghoul), to be ruddy.

Beer and Madler in their famous work Der Mond (1837) mention a surface feature of the moon after As-Sufi (Azophi). It is a mountainous ring twenty-six miles in diameter in the ninth section of the lunar map. Al-Sufi's influence in astronomy was substantial. It is reported that the Buwayh Sultan, Sharaf-al-Dawlah, became interested in astronomy because of Al-Suphi's influence.