Al-Malik Al-Ashraf (Mumahhid Al-Din) Umar Ibn Yūsuf Ibn Umar Ibn Alī Ibn Rasul (Arabic:عمر بن يوسف بن عمر بن علي بن رسول الغساني), known asUmar Ibn Yusuf (c. 1242 – 1296) was the thirdRasulid sultan, who ruled asAl-Ashraf Umar II. He was also amathematician,astronomer and physician.

Few biographical details about Al‑Malik al‑Ashraf ‘Umar are known.^[1] He was born in 1242 in Yemen,^{[note 1]} and he died in 1296.^[2] He excelled inastronomy, agriculture,veterinary science and medicine.^[1]

Al‑Ashraf ruled for as the thirdRasulid sultan for 21 months from 1295, succeeding after the end of the 46-year rule of his father,Al-Muzaffar Yusuf I. According to the historianDavid King. In 1266 he commanded a military raid on the Yemenese city ofHajjah. He was made governor ofal‑Mahjam [ar]. He was in charge of the highland city ofSanaa, now the capital of Yemen. For a period al‑Ashraf ruled as governor of the flood‑irrigated lands near al‑Mahjam, which was owned by his family.^[1]

Al‑Ashraf had six adult sons. Two of his daughters married sons of his younger brother and successor, al-Mu'ayyad Da'ud.^[1]

_{Data from theEncyclopaedia of Islam (1986)}^[3]

Al-Ashraf wrote the first description of the use of amagnetic compass for determining theqibla. His works onastronomy contain information on earlier sources.^[4]

In a treatise aboutastrolabes andsundials, al-Ashraf included information on the construction of a compass bowl (ṭāsa). He then uses the compass to determine the north point, themeridian (khaṭṭ niṣf al-nahār), and theqibla towardsMecca. This is the first mention of a compass in a medieval Islamic scientific text and its earliest known use as aqibla indicator, although al-Ashraf did not claim to be the first to use it for this purpose.^[4]

Al‑Ashraf astronomical treatise includes the names of local Yemeni star names.^[1]

Al-Ashraf'sMilh al‑Malâha is considered by the historianDavid King to be crucial for constructing the history of agriculture during the Rasulid era. The work, of which two copies are extant, is the earliest Rasulid treatise about agriculture. The exact title is not known.^[1]

The seven chapters of the treatise consider the knowledge of times for planting, transplanting, working the land and improving it; cereal crops (zar‘); pulses (qatânî), crops grown from seed (hubûb); the cultivation of flowering plants (al‑ashjâr al‑muthmira); aromatic plants (rayâhîn); growing vegetables (khadrâwât and (buqûlât); and methods of pest control (âfât). The text would have been primarily of use to Yemenese farmers and landowners; there is evidence that Al-Ashraf obtained some of his information from other lands, although no other texts are mentioned.^[1]

• Bosworth, C.E.; Van Donzel, E.; Heinrichs, W.P.; Lecompte, G., eds. (1986)."Rasulids".The Encyclopaedia of Islam. Vol. 8. Leiden:Brill Publishers. pp. 456–458.
• Schmidl, Petra G. (1997)."Two Early Arabic Sources On The Magnetic Compass".Journal of Arabic and Islamic Studies.1. Oslo:University of Oslo:81–132.doi:10.5617/jais.4547.ISSN 0806-198X.
• Schmidl, Petra G. (2007)."Ashraf: al-Malik al-Ashraf (Mumahhid al-Dīn) ʿUmar ibn Yūsuf ibn ʿUmar ibn ʿAlī ibn Rasūl". In Thomas Hockey; et al. (eds.).The Biographical Encyclopedia of Astronomers. New York: Springer. pp. 66–7.ISBN 9780387310220. (PDF version)

Wikimedia Commons has media related toAl-Ashraf Umar II.

• Ali, Abdul (1996).Islamic Dynasties of the Arab East: State and Civilization During the Later Medieval Times. M.D. Publications Pvt. Limited.ISBN 978-81753-3-008-5.
• King, David A. (1983).Mathematical Astronomy in Medieval Yemen: A Biobibliographical Survey. Undena Publications. p. 27.ISBN 978-08900-3-098-1.
• King, David A. (1985)."075 - Yemeni Astrolabe in NY Met 1985.pdf".Zeitschrift für Geschichte der Arabisch-Islamischen Wissenschaften.2:99–122.
• Suter, Heinrich (1900).Die Mathematiker und Astronomen der Araber und ihre Werke (in German). Leipzig: Teubner. p. 160.
• Varisco, Daniel Martin (1994).Medieval Agriculture and Islamic Science: the Almanac of a Yemeni Sultan. Washington, DC:University of Washington Press.ISBN 978-02959-7-378-4.
• "Astrolabe of 'Umar ibn Yusuf ibn 'Umar ibn 'Ali ibn Rasul al-Muzaffari".The Met.The Metropolitan Museum of Art. Retrieved2 February 2023.
• "Al-Malik al-Ashraf: Milḥ al-malāḥa fī ma'rifat al-filāḥa".The Filāḥa Texts Project. Retrieved3 February 2023.

• 1240s births
• 1296 deaths
• 13th-century Arab people
• 13th-century astronomers
• Astronomers of the medieval Islamic world
• Yemeni astronomers
• Monarchs of Yemen
• 13th-century monarchs in Asia
• Rasulid dynasty

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