Abd al-Rahman al-Sufi

Showing his diagram of the Gemini constellation with data on facing page

Showing his double diagram of the constellation of Cancer, the crab

'Abd al-Rahman al-Sufi (Persian: عبدالرحمن صوفی‎; 7 December 903 – 25 May 986), known as al-Sufi, was a Persian astronomer. The lunar crater Azophi and the minor planet 12621 Alsufi are named after him. Al-Sufi wrote his Book of Fixed Stars in 964, in text and pictures.

Biography

Al-Sufi was one of the nine noted Muslim astronomers. His name implies that he was a Sufi Muslim. He lived at the court of Emir Adud ad-Daula in Isfahan, Persia. He translated and expanded Greek astronomical works, especially the Almagest of Ptolemy. He made several corrections to Ptolemy's star-list and did his own brightness and magnitude estimates which often differed from those in Ptolemy's work.

He was a major translator into Arabic of the Hellenistic astronomy done mainly in Alexandria. This was the first attempt to connect the Greek with the traditional Arabic star names and constellations, which had been unrelated and overlapped in complicated ways.

Astronomy

The constellation Sagittarius from The Depiction of Celestial Constellations

He identified the Large Magellanic 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 colour, 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 astrolabe, finding numerous additional uses for it: he described over 1000 different uses, in areas as diverse as astronomy, astrology, horoscopes, navigation, surveying, timekeeping, Qibla, Salah prayer, etc.