ʿAlī ibn ʿĪsā al-Asṭurlābī

Not to be confused with ʿAlī ibn ʿĪsā al-Kahhal.

ʿAlī ibn ʿĪsā al-Asṭurlābī (Arabic: علي بن عيسى‎) was an Afro-Arab^{[citation needed]} astronomer and geographer of the 9th century. He wrote a treatise on the astrolabe and was an opponent of astrology. During the reign of al-Ma'mun, and together with Khālid ibn ʿAbd al‐Malik al‐Marwarrūdhī, he participated in an expedition to the Plain of Sinjar to measure the length of a degree, or the circumference of the Earth.^[1] He measured the Earth's circumference, getting a result of 40,248 km (or, according to other sources, 41,436 km).^{[citation needed]}

Notes

1. ^ Bolt 2007.

References

• Bolt, Marvin (2007). "ʿAlī ibn ʿĪsā al‐Asṭurlābī". In Thomas Hockey et al. The Biographical Encyclopedia of Astronomers. New York: Springer. p. 34. ISBN 9780387310220. http://islamsci.mcgill.ca/RASI/BEA/Ali_ibn_Isa_al-Asturlabi_BEA.htm.  (PDF version)

See also

• List of Arab scientists and scholars

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Name	Isa, Ali Ben
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