Muḥyī al‐Milla wa al‐Dīn Yaḥyā Abū ʿAbdallāh ibn Muḥammad ibn Abī al‐Shukr al‐Maghribī al‐Andalusī (Arabic:محيي الدين المغربي;c. 1220 – June 1283), referred to in sources asMuhyi l'din, was anastronomer,astrologer andmathematician of theIslamic Golden Age. He belonged to the group of astronomers associated with theMaragheh observatory in theIlkhanate, most notablyNasir al-Din al-Tusi. In astronomy,Muhyi l'din carried out a large‐scale project of systematic planetary observations, which led to the development of several new astronomical parameters.^[1]

Muhyi l'din died inMaragheh in modern-day Iran in June 1283.^[1]

Muhyi al-Dīn al-Maghribī was born inc. 1220 inal-Andalus.^[2] He worked for theAyyubid sultanAn-Nasir Yusuf inDamascus.^{[3][page needed]} This relationship was ultimately cut short when the sultan was killed by the Mongols in theSiege of Aleppo in 1257. He was then sent to theobservatory at Maragheh.^{[3][page needed]}

The Maraghehobservatory was founded in theIlkhanate, a part of theMongol Empire,^[4]Muhyi l'din went to Maragheh in 1258 as a guest of theMongol rulerHulagu Khan, where from 1259 he was involved, along withNasir al-Din al-Tusi, in its construction. The observatory was completed in 1262.^[2]

At Maragheh,Muhyi l'din observed up to a total of eight of the brightest stars,^{[dubious –discuss]} of which he used the latitudes collected to compare with the values within ancient computations.^{[5][page needed]} He concluded that the difference between his latitudes and ancients were not substantial, and any inconsistences were in fact due to the observations and not the subject itself. In hisTalkhīṣ al‐Majisṭī, he commentated on Ptolemy's Almagest, presenting his own observations and hypothesizes in addition with it. For instance, Muhyi l'din supposed that theprecession would only occur in a motion that was uniform and continuous at a rate that was 1° for ever 66 years from his systematic stellar observations.^{[5][page needed]}

An extantmanuscript by Muhyi l'din details of observations made from 1262 to 1274.^[2] He continued to work on his observations at Maragheh until his death in 1283.^{[3][page needed]}

Muhyi l'din considered the problem ofdoubling the cube, which he approached means of a method devised by the Greek mathematicianHippocrates of Chios.^[2]

Muhyi l'din's known works on astronomy include:^[1]

• Tasṭīḥ al‐asṭurlāb, a description of the construction and use of theastrolabe;
• Maqāla fī istikhrāj taʿdīl al‐nahār wa saʿat al‐mashriq wa‐ʾl‐dāʾir min al‐falak bi‐ṭarīq al‐handasa, a description of thegeometrical methods used to determine themeridian line, the rising amplitude, and the revolution of the sphere;
• Risālat al‐Khaṭā wa‐ʾl‐īghūr, a chronological work on theChinese calendar, which was later translated fromArabic andPersian intoChinese.
• Threezījes:
  • Tāj al‐azyāj wa‐ghunyat al‐muḥtāj (The Crown of Astronomical Handbooks), also known asal‐muṣaḥḥaḥ bi‐adwār al‐anwār maʿa al‐raṣad wa‐ʾl‐iʿtibār;
  • Adwār al‐anwār madā al‐duhūr wa‐ʾl‐akwār, which contains astronomical observations carried out by Muhyi l'dinin Marāgha;
  • ʿUmdat al‐ḥāsib wa‐ghunyat al‐ṭālib;
• Three commentaries onPtolemy'sAlmagest:
  • Talkhīṣ al‐Majisṭī (Compendium of the Almagest), based on his observations carried out between 1264 and 1275;
  • Khulāṣat al‐Majisṭī (Summary of the Almagest);
  • Muqaddimāt tataʿallaq bi‐ḥarakāt al‐kawākib (Prolegomena on the Motion of the Stars), which contains five geometric premises on the planetary motions in theAlmagest.

Muhyi l'din's astrological works were mainly devoted tohoroscopes and planetaryconjunctions, used to tell the future.^[1]

Muhyi l'din's notable works intrigonometry wereThe Book on the Theorem of Menelaus andTreatise on the Calculation of Sines.^[2] He is known for his commentaries onancient Greek mathematical works, in particular, his commentary on Book XV ofEuclid's Elements, which discussed measurements of theregular polyhedra.^[2][6] Muhyi l'din's writings on trigonometry contain some elements that are original.^[1]

In his treatise on the calculation ofsines, Muhyi l'dininterpolated a value for the sine of one degree; a more accurate value was not obtained until the 15th century, when the mathematiciansQāḍī Zāda al-Rūmī andJamshid al-Kashi tackled the problem. Whilst working on the sines, Muhyi l'din used the methods devised byArchimedes to find an approximate value forpi.^[2]

• Comes, Mercè (2007)."Ibn Abī al‐Shukr: Muḥyī al‐Milla wa‐ʾl‐Dīn Yaḥyā Abū ʿAbdallāh ibn Muḥammad ibn Abī al‐Shukr al‐Maghribī al‐Andalusī [al‐Qurṭubī]". In Hockey, Thomas; et al. (eds.).Biographical Encyclopedia of Astronomers. New York:Springer Publishers. pp. 548–549.doi:10.1007/978-0-387-30400-7_1433.ISBN 978-1-4419-9918-4. (PDF version)
• Mozaffari, S. Mohammad (2014). "Muḥyī al-Dīn al-Maghribī's lunar measurements at the Maragha observatory".Archive for History of Exact Sciences.68 (1):67–120.doi:10.1007/s00407-013-0130-4.ISSN 0003-9519.JSTOR 24569613.
• Roberts, Victor (1966). "The Planetary Theory of Ibn al-Shatir: Latitudes of the Planets".Isis.50 (3). Chicago: The University of Chicago Press:208–219.JSTOR 227960.
• Mozaffari, S. Mohammad (2016). "A forgotten solar model".Archive for History of Exact Sciences.70 (3).Springer Nature:267–291.doi:10.1007/s00407-015-0167-7.ISSN 0003-9519.JSTOR 24913461.
• O'Connor, J.J.; Robertson, E.F. (1999)."Muhyi l'din al-Maghribi".MacTutor.University of St Andrews. Retrieved28 February 2023.
• Tekeli, Sevim (1981). "Muḥyi 'L-Dīn Al-Maghribī (Muḥyi 'I-Milla Wa 'L-Dīn Yaḥyā Ibn Muḥammad Ibn Abi 'I-Shukr Al-Maghribī' Al-Andalusī)". In Gillispie, Charles Coulston; Holmes, Frederic Lawrence (eds.).Dictionary of Scientific Biography. Vol. 9. New York: Scribner.OCLC 755137603.

• Dorce, Carlos (2003)."The Taj al-azyāj of Muḥyī al-Din al-Maghribī (d. 1283): methods of computation".Suhayl. International Journal for the History of the Exact and Natural Sciences in Islamic Civilisation.3.University of Barcelona:193–212.ISSN 1576-9372 – via RACO (Catalan Journals with Open Access).

• Digitized manuscript (Tasṭīḥ al-asṭurlāb) - Folios 1A-7B, Sprenger 1876 (Berlin State Library)

• 1283 deaths
• Astronomers from al-Andalus
• Astrologers of the medieval Islamic world
• Mathematicians from al-Andalus
• 13th-century astronomers
• 13th-century astrologers
• 13th-century mathematicians
• 13th-century people from al-Andalus
• People from Córdoba, Spain
• 13th-century Iranian astronomers

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