From: Thomas Hockey et al. (eds.). The Biographical Encyclopedia of Astronomers, Springer Reference. New York: Springer, 2007, pp. 10 Courtesy of Springer.

David A. King

Abū al‐ʿUqūl: Abū al‐ʿUqūl Muḥammad ibn Aḥmad al‐Ṭabarī

FlourishedYemen, circa1300

Abū al‐ʿUqūl was the leading astronomer in Taiz, Yemen, circa 1300. His epithet al‐Ṭabarī indicates that he or his family came originally from northern Iran. He was a contemporary of the ruler Ashraf and Muḥammad ibn Abī Bakr al‐Fārisī, the latter also of Iranian stock. No details of Abū al‐ʿUqūl's life are known to us beyond the fact that he was the first teacher of astronomy appointed at the Muʾayyadiyya Madrasa in Taiz by the Sultan al‐Muʾayyad, brother and successor of al‐Ashraf.

Abū al‐ʿUqūl compiled an astronomical handbook (Arabic: zīj) for the Yemen and was not shy about admitting to having taken most of it from other sources; indeed, he called his work al‐Zīj al‐mukhtār min al‐azyāj (The Zīj culled from other Zījes). In fact, the work is based heavily on the Ḥākimī Zīj of the 10th‐century Egyptian scholar Ibn Yūnus. What is original are the various tables of spherical astronomical functions for latitudes in the Yemen, and it is clear that spherical astronomy was the author's forte.

Abū al‐ʿUqūl compiled the largest single medieval corpus of tables for astronomical timekeeping for a specific latitude, with over 100,000 entries. This corpus, entitled Mirʾāt al‐zamān (Mirror of Time), is computed for latitude 13° 37', an excellent value for Taiz (accurately 13° 35'!) derived by either Abū al‐ʿUqūl or al‐Fārisī, and obliquity 23° 35'. In addition to tables of the hour angle and the time since sunrise for each degree of solar altitude and solar longitude, such as are found in the Cairo corpus associated with Ibn Yūnus, there are tables displaying the longitude of the ascendant or horoscopus as a function of solar altitude and longitude, and others displaying the altitude of various fixed stars at daybreak as a function of the ascendant. The inspiration for the tables associated with the ascendant seems to come from Iraq or Iran, where such tables are attested, rather than from Egypt. Abū al‐ʿUqūl's extensive tables are known from a unique manuscript copied in Mocca on the Red Sea coast of Yemen in 1795. To what extent they were used over the centuries is unclear.

Abū al‐ʿUqūl also prepared an almanac in which astronomical phenomena were associated with aspects of agricultural practice.

Selected References

Abū al‐ʿUqūl. Al‐Zīj al‐mukhtār min al‐azyāj. London, British Library, MS Or. 3624. (A unique copy.)

———. Mirʾāt al‐zamān. Berlin, Deutsche Staatsbibliothek, Ahlwardt MS 5720. (A unique copy.)

King, David A. (1983). Mathematical Astronomy in Medieval Yemen: A Biobibliographical Survey. Malibu: Undena Publications, pp. 30–32 (no. 9).

——— (2004). In Synchrony with the Heavens: Studies in Astronomical Timekeeping and Instrumentation in Medieval Islamic Civilization. Vol. 1, The Call of the Muezzin (Studies I–IX). Leiden: E. J. Brill. I–2.1.2, 3.1.1, 3.3.2, 4.2.6, 4.5.1, and II–12.1.

Varisco, Daniel Martin (1994). Medieval Agriculture and Islamic Science: The Almanac of a Yemeni Sultan. Seattle: University of Washington Press, pp. 10–11.

References in ISMI