AḤMAD B. MOḤAMMAD NEHĀVANDĪ, 2nd/8th century ʿAbbasid astronomer. The fame of this author is due almost entirely to Ebn Yūnos’s statement (al-Zīǰ, pp. 156-59) that he knew of no observations to determine the mean motion of the sun between the time of Ptolemy and that of the authors of al-Zīǰ al-momtaḥan save those made by Aḥmad b. Moḥammad Nehāvandī at Jondīšābūr in the days of Yaḥyā b. Ḵāled b. Barmak; the results of these observations were recorded in Aḥmad’s al-Zīǰ al-moštamel. Since Yaḥyā was Hārūn al-Rašīd’s vizier from 786 to 803, Nehāvandī presumably made his observations in the 790s. Thus he is probably not identical, as Suter and Sezgin have suggested, with Aḥmad b. Moḥammad, the calculator mentioned by Ebn al-Nadīm (p. 282). Among the three works of the latter is a Ketāb fi’l-Nīl (“Book concerning the Nile [?]”) addressed to a certain Moḥammad b. Mūsā. Whether this Moḥammad is the famous Ḵᵛārazmī, who flourished during the caliphate of Maʾmūn, or the son of Mūsā b. Šāker, who belonged to the following generation, either individual is too late to be associated with Nehāvandī. It would have been unusual for a Persian scholar to compose a book about the Nile.


See also Ebn Yūnos, al-Zīǰ al-Ḥākemī, in Caussin de Perceval, “Le livre de la Grande Table Hakémite,” Notices et extraits 7, an 12, pp. 16-240.

E. S. Kennedy, A Survey of Islamic Astronomical Tables, Philadelphia, 1956, p. 124 (no. 1).

A. Sayili, The Observatory in Islam, Ankara, 1960, pp. 50-51. Sezgin, GAS V, pp. 226-27.

Suter, Mathematiker, p. 10, no. 18.

(D. Pingree)

Originally Published: December 15, 1984

Last Updated: July 28, 2011

This article is available in print.
Vol. I, Fasc. 6, p. 653

Cite this entry:

David Pingree, “AḤMAD NEHĀVANDĪ,” Encyclopædia Iranica, I/6, p. 653; an updated version is available online at http://www.iranicaonline.org/articles/ahmad-b-20 (accessed on 19 March 2014).