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| Zīj-i Ilkhani | |
|---|---|
| Name | Zīj-i Ilkhani |
| Author | Naṣir al-Dīn al-Ṭūsī |
| Country | Khwarezmian Empire / Ilkhanate |
| Language | Persian and Arabic |
| Subject | Astronomy, Tables |
| Published | 13th century (c. 1272) |
Zīj-i Ilkhani is a 13th-century astronomical handbook and set of tables compiled by Naṣir al-Dīn al-Ṭūsī for the Ilkhanate court under Hülegü. Commissioned in the wake of the Mongol conquests, it synthesized earlier Islamic, Indian, and Hellenistic traditions into a work used for ephemerides, timekeeping, and calendrical calculations across the Islamic world and beyond. The work influenced observatories, nautical practice, and later astronomers in Persia, Anatolia, India, and Europe.
Naṣir al-Dīn al-Ṭūsī completed the Zīj under the patronage of Hülegü and the Ilkhanate elite shortly after the fall of Baghdad and during contacts with figures associated with the Mongol court, including Kitbuqa and Möngke. The project was enabled by the observatory at Maragha, directed by al-Ṭūsī and supported by scholars from diverse milieus such as Ibn al-Shatir, al-Battānī, and al-Khujandī. Influences trace to earlier centers like Baghdad's Bayt al-Ḥikma, Isfahan, Nishapur, Samarkand, and Indian centers linked to the Sanskrit astronomical tradition and works by Brahmagupta and Aryabhata. Contacts with Byzantine and Armenian scholars, Seljuk administrators, and Persian bureaucrats shaped resources and patronage networks, while correspondence connected the project to Cairo, Damascus, Mosul, Tabriz, and Konya.
The Zīj contains planetary tables, solar and lunar tables, eclipses, trigonometric tables, and tables for calendrical conversion adapted to the Ilkhanid meridian. It incorporates models and parameters refined from Ptolemy, al-Battānī, al-Zarqālī, and Indian zīj works such as the Siddhāntas, alongside practical material used in chancelleries like those of the Abbasids, Fatimids, Seljuks, and Samanids. Specific items include mean motions, true positions, equation of time, and tables for qibla and prayer times relevant to cities from Cairo to Samarra, from Rayy to Balkh, and from Constantinople to Delhi. The compilation was used by Ottoman, Timurid, and Mughal astronomers; later readers included Ulugh Beg, al-Kāshī, ibn al-Banna, and Tycho Brahe via indirect transmission.
Al-Ṭūsī employed mathematical techniques such as trigonometric interpolation, spherical astronomy, and the Ṭūsī-couple (a geometric device for generating linear motion from uniform circular motions). Instruments associated with the work and the Maragha observatory include the armillary sphere, sextant-like quadrants, mural instruments, astrolabes, and mechanical models related to innovations later found in the works of al-Jazari and the repertoire of instrument makers in Cairo, Damascus, and Venice. The methodological lineage ties to Ptolemaic methods from the Almagest, to innovations by Islamic astronomers like al-Khwarizmi, al-Battānī, and Ibn Sahl, and to later procedures appearing in Ottoman madrasa curricula and Mughal observatories at Delhi and Jaipur.
The Zīj shaped observational programs and computational astronomy in the Ilkhanate, Timurid, Ottoman, and Mughal realms, influencing Ulugh Beg's Samarqand school, al-Kāshī's numerical techniques, and calendrical reform debates in Cairo and Istanbul. Its parameters were used in planetary tables circulating in Hebron, Fez, Granada, and Lisbon; translations and adaptations reached Latin medieval scholarship, affecting scholars in Toledo, Paris, and Padua and filtering into the Renaissance through figures linked to the Venice and Genoa book trades. The Ṭūsī-couple anticipated later discussions in Copernican and Keplerian contexts and informed instrument design referenced by Tycho Brahe and Johannes Hevelius via transmission of ideas through Safavid, Ottoman, and European networks.
Manuscripts of the Zīj survive in collections in libraries such as the Süleymaniye, Topkapı, British Library, Bibliothèque nationale de France, Biblioteca Nazionale Marciana, Bodleian Library, and libraries in Tehran, Tbilisi, and Cairo. Copyists and commentators included figures from Shiraz, Herat, Isfahan, and Cairo; notable copyists and annotators drew links to works by Ibn Yūnus, al-Sūfī, and al-Tūfī. Printed and critical editions emerged in the 19th and 20th centuries in scholarship centers like Saint Petersburg, Leiden, and Munich, with editions and catalogues prepared by orientalists and historians associated with institutions such as the École Pratique, Humboldt Universität, and the Royal Asiatic Society.
Contemporary studies situate the Zīj within histories by historians and historians of science including Edward Said in cultural context, historians such as Paul Lombardi, George Saliba, David King, and A. I. Sabra in astronomical analysis, and philologists in Tehran, Paris, and London producing critical editions. Research addresses the computational procedures, transmission pathways through Safavid and Ottoman archives, the role of Maragha as a knowledge hub compared with Samarkand and Constantinople, and the Zīj’s influence on later instrument-makers. Ongoing projects at universities and observatories in Istanbul, Leiden, Princeton, and Tehran examine manuscript variants, numerical reconstructions, and comparative studies with the Almagest, Siddhāntas, Zij-i Sultani, and Samarqand observations, contributing to broader understanding of medieval scientific networks involving Baghdad, Cairo, Delhi, Granada, and Venice.
Category:Astronomical tables Category:Naṣir al-Dīn al-Ṭūsī Category:Ilkhanate