Al-Battani ălˌbətēˈnēəs [key], b. before 858, d. 929, Arab astronomer and mathematician. He is best known in astronomy for his improvements and corrections of the Ptolemaic tradition. His Kitab al-Zij, which in Latin translation was very influential in the Middle Ages and the Renaissance, contains an elaborate set of astronomical tables and discusses a wide range of practical problems in spherical astronomy, some of which were devised for the purpose of solving related astrological problems. He recognized the possibility of an annular eclipse of the sun and obtained the very accurate value of 23°35′ for the obliquity of the ecliptic.

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