Al-Sufi

Al-Sufi

Abd al-Rahman al-Sufi (Persian: عبدالرحمن صوفی, December 903 – 25 May 986) was a Persian astronomer who lived in the 10th century.

He is also known as Abd al-Rahman Abu al-Husayn, Abd al-Rahman Sufi, Abdurrahman Sufi, and in the Western world as 'Azophi'; the lunar crater Azophi and the minor planet 12621 Alsufi are named after him.

Biography

Abd al-Rahman al-Sufi was born in 903 in the city of Rayy in Iran. He lived at the court of Emir Adud al-Dawla in Isfahan, Iran, and became known for the star catalogue he prepared drawing on Ptolemy's Almagest. In this catalogue, after introducing the stars found in the forty-eight constellations and reporting their positions and magnitudes in the sky, he gave the Arabic equivalents of the star names mentioned in the Almagest, thereby filling an important gap in Arabic on this subject. The terms proposed by al-Sufi were later used by both Eastern and Western astronomers, and 94 of them entered the modern astronomical literature. As a result of different pronunciations, his name appears in Western languages in various forms such as 'Azophi', 'Ilbermosofim', 'Jeber Mosphim' and 'Abuhassin'.

The units that al-Sufi used to measure the distances of celestial bodies — such as rumh = 14B = the distance of Andromedae and Pegasi; dhira' = 1/6 rumh = ZB 20; shibr = 1/3 dhira'; isba' = 1/32 dhira' — were used very soundly in determining distances.

Al-Sufi drew each constellation in two ways — once as it appears in the sky and once as it would appear on the celestial globe — and then, by giving the longitude, latitude, magnitude and colour of each star, he produced a tabular catalogue arranged by constellation. The beginning of this star table is the first day of the year 1276 of the calendar of Alexander, corresponding to 20 Ramadan 353 AH, 30 September 964 in the Gregorian calendar.

He found the longitudes by adding to the longitudes established by Ptolemy a fixed amount of 42 degrees 41 minutes in total, at the rate of 1 degree for every 66 years. Whereas in the time of Caliph al-Ma'mun, Ptolemy's table used in preparing the "Zij al-Mumtahan" had been arranged by adding 1 degree per 100 years to the values given by Menelaus. It is accepted that the tradition of preparing cosmographic maps, which began with Ptolemy, reached our age by passing through al-Sufi.

Sources

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