From: Thomas Hockey et al. (eds.). The Biographical Encyclopedia of Astronomers, Springer Reference. New York: Springer, 2007, pp. 474-475
Born Rayy, (Iran), February 766 or March 763
Died Ṭūs, (Iran), 24 March 809
Hārūn al‐Rashīd, who reigned from 786 to 809, was the third son of Caliph al‐Mahdī (died: 785) and the second son of a Yemeni slave girl called Khayzurān, freed and married by his father in 775/776. His education lay in the hands of the Barmakid Yaḥyā ibn Khālid (died: 805, Baghdad; killed on the caliph's order). In 782, Harun was appointed governor of the northern African, Egyptian, Syrian, Armenian, and Azerbaijanian territories of the ʿAbbāsid Empire, and declared second in succession. The powers behind this move were his mother and Yaḥyā ibn Khālid, who became the head of administration in these territories. In 786, in his early 20s, Hārūn became caliph after both his father and his brother died under suspicious circumstances. He chose as his Supreme Vizier Yaḥyā ibn Khālid who, together with his two sons Faḍl and Jaʿfar, ruled the empire for 17 years. Hārūn subsequently replaced them with groups entirely loyal to himself, mostly eunuchs and clients. Hārūn's reign was characterized by many serious uprisings against the caliphal power, although in A Thousand and One Nights it is portrayed as a period of glamour and splendor.
With regard to the arts and sciences, Hārūn continued the policies of his predecessors, although according to Arabic sources such as Ibn al‐Nadīm's Fihrist these policies seem rather to have been instigated by his Barmakid vizier. During Hārūn's reign, a library was founded at the court with a director and several collaborators. Its scope and profile have been the subject of considerable debate in the literature. It apparently was closely related to the process of translating ancient texts into Arabic. D. Gutas has pointed out that the available evidence for this relationship privileges translations of Persian texts. He emphasizes that Ibn al‐Nadīm's report about a translation of the Almagest linked to this library is the only explicit reference to a possible contribution of the library to translations of Greek texts. Ibn al‐Nadīm claims that the director of the library, a certain Salm, and a second person known only as Abū Ḥassān, were called to court by the vizier in order to explain Ptolemy's book. This event caused Salm and Abū Ḥassān to employ the best‐known translators to translate Ptolemy's Almagest, check their translation, and make sure of its good literary style and accuracy (Ibn al‐Nadīm, 2: 639). Unfortunately, we today know next to nothing about these translators or this translation; in any event this translation was most likely superseded by several others in the 9th century that may well have depended on it to some degree.
Gutas, Dimitri (1998). Greek Thought, Arabic Culture: The Graeco‐Arabic Translation Movement in Baghdad and Early ʿAbbāsid Society (2nd–4th/8th–10th centuries). London: Routledge.
Ibn al‐Nadīm (1970). The Fihrist of al‐Nadīm: A Tenth‐Century Survey of Muslim Culture, edited and translated by Bayard Dodge. 2 Vols. New York: Columbia University Press.
Omar, F. (1971). “Hārūn al‐Rashīd.” In Encyclopaedia of Islam. 2nd ed. Vol. 3, pp. 232–234. Leiden: E. J. Brill.