ABU’L-ḤASAN AHWĀZĪ, astronomer, fl. after ca. 215/830. He is known through citations by Bīrūnī. He used the revolutions of the planets in a mahāyuga according to the system of the Indian Āryabhaṭa (Bīrūnī, India, Hyderabad [Deccan], 1958, p. 357; tr. E. Sachau, London, 1910, II, p. 19; cf. Hāšemī, The Book of the Reasons behind Astronomical Tables, tr. F. I. Haddad and E. S. Kennedy, comm. by Kennedy and D. Pingree, Delmar, N.Y., 1981). He criticized al-Zīǰ al-Sendhend by Ḵᵛārazmī (d. ca. 232/847; Bīrūnī, Resāla, ed. P. Kraus, Paris, 1936, p. 30); and he commented on Ptolemy’s method of finding a shadow using chords instead of sines (Bīrūnī, Shadows, pt. 2 of Rasāʾel al-Bīrūnī, Hyderabad [Deccan], 1948, ed., pp. 56-57; tr. and comm. by E. S. Kennedy, 2 vols., Aleppo, 1976: tr., pp. 95-96; comm., p. 42). Ahwāzī may be identical with the Abu’l-Ḥasan who observed the noon altitude of the sun at Baghdad on 1 May and 3 August 832 (Bīrūnī, Taḥdīd al-amāken, ed. P. Bulgakov, Cairo, 1964, p. 86; tr. J. Ali, Beirut, 1967, p. 56; comm. E. S. Kennedy, Beirut, 1973, p. 30). It is less likely that he is the secretary Abu’l-Ḥasan Aḥmad b. Ḥosayn Ahwāzī. The latter traveled to Constantinople and wrote Ketāb maʿāref al-Rūm (“Book of intelligences on the Byzantines”), in which he reported on such matters as the ecclesiastical hierarchy and the christening ceremony (Bīrūnī, Āṯār al-bāqīya, pp. 289, 293; Chronology, pp. 284, 288-89).
See also Sezgin, GAS VI, p. 233.
Originally Published: December 15, 1983
Last Updated: August 21, 2012
This article is available in print.
Vol. I, Fasc. 3, p. 302
David Pingree, “Abu’l-Ḥasan Ahwāzi,” Encyclopædia Iranica, I/3, p. 302; an updated version is available online at http://www.iranicaonline.org/articles/abul-hasan-ahwazi-astronomer-fl (accessed on 31 January 2014).