(868--929 A.D.)

Abu Abdallah Muhammad Ibn Jabir Ibn Sinan al-Battanial-Harrani was born around 858 A.D. in Harran, and according toone account, in Battan, a State of Harran. Battani was first educatedby his father Jabir Ibn San'an al-Battani, who was also a well-knownscientist. He then moved to Raqqa, situated on the bank of theEuphrates, where he received advanced education and later onflourished as a scholar. At the beginning of the 9th century, hemigrated to Samarra, where he worked till the e nd of his life in929 A.D. He was of Sabian origin, but was himself a Muslim.

Battani was a famous astronomer, mathematician and astro-loger. He has been held as one of the greatest astronomists of Islam.He is responsible for a number of important discoveries inastronomy, which was the result of a long care er of 42 years ofresearch beginning at Raqqa when he was young. His well-knowndiscovery is the remarkably accurate determination of the solaryear as being 365 days, 5 hours, 46 minutes and 24 seconds, whichis very close to the latest estimates. He found t hat the longitude ofthe sun's apogee had increased by 16° , 47' since Ptolemy. Thisimplied the important discovery of the motion of the solar apsidesand of a slow variation in the equation of time. He did not believein the trapidation of the equinoxe s, although Copernicus held it.

Al-Battani determined with remarkable accuracy the obliquityof the ecliptic, the length of the seasons and the true and mean orbitof the sun.

He proved, in sharp contrast to Ptolemy, the variation of theapparent angular diameter of the sun and the possibility of annulareclipses. He rectified several orbits of the moon and the planetsand propounded a new and very ingenio us theory to determinethe conditions of visibility of the new moon. His excellent observa-tions of lunar and solar eclipses were used by Dunthorne in 1749to determine the secular acceleration of motion of the moon. Healso provided very neat solutions by m eans of orthographic projec-tion for some problems of spherical trigonometry.

In mathematics, he was the first to replace the use of Greekchords by sines, with a clear understanding of their superiority.

He also developed the concept of cotangent and furnished theirtable in degrees.

He wrote a number of books on astronomy and trigonometry.His most famous book was his astronomical treatise with tables,which was translated int o Latin in the 12th century and flourishedas De scienta stellerum De numeris stellerum et motibus. An old translation of this is available of the Vatican. His Zij was, infact, more accurate than all others written by that time.

His treatise on astronomy was extremely influential in Europetill the Renaissance, with translations available in several languages.His original discoveries both in astronomy and trigonometry were ofgreat consequence in the develo pment of these sciences.

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from: http://www.oman-net.com/msp/battani.htm