Wednesday, March 6, 2013

'Abd al-Rahman ibn 'Umar al-Sufi

‘Abd al-Rahman ibn ‘Umar al-Sufi (b. December 7, 903, Rey, Iran - d. May 25, 986, Shiraz) was a Persian astronomer at the court of the Buyids whose best known work is a description of the fixed stars.  

Al-Sufi published his famous Book of Fixed Stars in 964, describing much of his work, both in textual descriptions and pictures. Al-Sufi's Book of Fixed Stars (Kitab al-Kawatib al-Thabit al-Musawwar) includes a catalog of 1,018 stars, giving their approximate positions, magnitudes, and colors. 
The lunar crater Azophi and the minor planet (12621) Al-Sufi are named after him.

Al-Sufi lived at the court of Emir Adud ad-Daula in Isfahan, 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, 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.

Al-Sufi identified the Large Magellanic Cloud, which is visible from Yemen, but not from Isfahan.  The Large Magellanic Cloud 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, describing it as a "small cloud."

Al-Sufi 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, al-Sufi 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.

Al-Sufi also first described over 1000 different uses of an astrolabe, in areas as diverse as astronomy, astrology, horoscopes, navigation, surveying, timekeeping, Qibla, and Salah prayer.

Alternative names include:

'Abd al-Rahman Abu al-Husayn 

'Abd al-Rahman al-Sufi 
'Abd al-Rahman ibn 'Umar al-Sufi
'Abd ar-Rahman as-Sufi
Abu al-Husayn
Abu al-Husayn, 'Abd al-Rahman
Al-Husayn, 'Abd al-Rahman Abu
Al-Sufi, 'Abd al-Rahman
Al-Sufi, 'Abd al-Rahman ibn 'Umar 
As-Sufi, 'Abd ar-Rahman
Azophi see ‘Abd al-Rahman ibn ‘Umar al-Sufi

Husayn, 'Abd al-Rahman Abu al-
Husayn, al-
Ibn 'Umar al-Sufi
Ibn 'Umar al-Sufi, 'Abd al-Rahman
Sufi, 'Abd al-Rahman al-
Sufi, 'Abd al-Rahman ibn 'Umar al-
Sufi, 'Abd ar-Rahman as-
Sufi, as-

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