Abd Al-Rahman Al Sufi

December 9, 903 in Rey, Iran – May 25, 986 in Shiraz, Iran

Biography

He was one of the famous nine Muslim astronomers. His name implies that he was from a Sufi Muslim background. He lived at the court of Emir Adud ad-Daula in Ispahan, Persia, and worked on translating and expanding Greek astronomical works, especially the Almagest of Ptolemy. He contributed several corrections to Ptolemy's star list and did his own brightness and magnitude estimates which frequently deviated from those in Ptolemy's work.

He was a major translator into Arabic of the Hellenistic astronomy that had been centered in Alexandria, Egypt the first to attempt to relate the Greek with the traditional Arabic star names and constellations which were completely unrelated and overlapped in complicated ways.

Discovery/Contributions

He identified the Large Magelletic Cloud, which is visible from Yemen, though not from Isfahan; it was not seen by Europeans until Magellan's voyage in the 16th century. He also made the earliest recorded observation of the Andromeda Galaxy in 964 AD; describing it as a "small cloud". These were the first galaxies other than the Milky Way to be observed from Earth.

He observed that the ecliptic plane is inclined with respect to the celestial equator and more accurately calculated the length of the tropical year. He observed and described the stars, their positions, their magnitudes and their color, setting out his results constellation by constellation. For each constellation, he provided two drawings, one from the outside of a celestial globe, and the other from the inside (as seen from the earth).

Al-Sufi also wrote about the astroble, finding numerous additional uses for it: he described over 1000 different uses, in areas as diverse as astronomy, astrology, horoscopes, Navigation, survaying, timekeeping, Qibla, Salat prayer, etc