From: Thomas Hockey et al. (eds.). The Biographical Encyclopedia of Astronomers, Springer Reference. New York: Springer, 2007, pp. 567-568

Courtesy of

Ibn al‐alā: Najm al‐Dīn Abū al‐Futū Amad ibn Muammad ibn al‐Sarī ibn al‐alā

Paul Kunitzsch

BornSumaysā (Samsat, Turkey) or Hamadan (Iran)

DiedDamascus (Syria), 1154

Ibn al‐alā was famous for his acute understanding and critique of several Greek scientific texts that had been translated and were circulating in Arabic. By profession, Ibn al‐alā was a doctor. After studying and beginning his career in Baghdad, he is said to have been appointed court‐physician in Mārdīn at the court of the local ruler. He later settled in Damascus, where he died.

Especially of astronomical interest is his critique of the transmission of the coordinates in Ptolemy's star catalog (Almagest VII.5–VIII.1, dating from circa 150). He knew and used five different translations of the Almagest: one in Syriac and four in Arabic. For 88 of Ptolemy's 1,025 stars, Ibn al‐alā notes the mistakes in the transmitted coordinates and proposes, for most of them, better values found by him by observation and by comparison with the celestial globe. Another text relevant for astronomy is his Treatise on Projection. Projection here refers to the projection of the surface of the sphere on to a plane, a procedure that was of fundamental importance for the development and the construction of the astrolabe; Ptolemy's text on this topic, the Planisphaerium, had also been translated into Arabic. Other critical works of Ibn al‐alā deal with mathematical and philosophical problems. But most of his writings are still unpublished and unstudied.

Selected References

Ibn al‐alāḥ (1975). Zur Kritik der Koordinatenüberlieferung im Sternkatalog des Almagest, edited by Paul Kunitzsch. Göttingen: Vandenhoeck und Ruprecht. (Text, translation, and study.)

Lorch, Richard (2000). “Ibn al‐alāḥ's Treatise on Projection: A Preliminary Survey.” In Sic itur ad astra: Studien zur Geschichte der Mathematik und Naturwissenschaften. Festschrift für den Arabisten Paul Kunitzsch zum 70. Geburtstag, edited by Menso Folkerts and Richard Lorch, pp. 401–408. Wiesbaden: Harrassowitz Verlag.