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<p>This paper investigates Muḥyī al‑Dīn al‑Maghribī’s measurements of Saturn at the Maragha observatory (northwestern Iran, 13<sup>th</sup> century), preserved in Chapters 2–5 of Book VIII of his <i>Talkhīṣ al‑Majisṭī</i> (<i>The Compendium of the</i> Almagest). Employing Ptolemy’s iterative three‑point method as described in <i>Almagest</i> X and XI, he measured Saturn’s orbital elements (eccentricity and the longitude of the apogee) from three observations conducted near the planet’s opposition to the mean Sun on 25 October 1263, 9 December 1266, and 27 February 1273 (with longitudinal errors not exceeding 1/6°). He obtained an eccentricity of 3;15 (radius of orbit = 60), a value already encountered in Ptolemy’s <i>Canobic Inscription</i>, and a longitude of the apogee of 258;38° in 1273. A calculational mistake prevented him from measuring the more accurate value of 3;23 for the eccentricity; nevertheless, his apogee longitude stands as the most precise determination in the Islamic astronomical tradition. The accuracy of his values for the Ptolemaic parameters of Saturn and the quantitative outcomes of his theory are examined comprehensively and comparatively with all other known theories established in the late Islamic period, especially Saturn’s theory laid out in the <i>Īlkhānī zīj</i>. As a technical case study, this investigation furnishes new insights into the nature of observational practice and theoretical innovation in the medieval Islamic period.</p>

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Saturn observations and measurements at the Maragha observatory: error, success, and comparative study in historical context

  • 期刊论文

  • 发表日期：

    2026年6月24日

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  • Seyyed Mohammad Mozaffari

摘要

This paper investigates Muḥyī al‑Dīn al‑Maghribī’s measurements of Saturn at the Maragha observatory (northwestern Iran, 13th century), preserved in Chapters 2–5 of Book VIII of his Talkhīṣ al‑Majisṭī (The Compendium of the Almagest). Employing Ptolemy’s iterative three‑point method as described in Almagest X and XI, he measured Saturn’s orbital elements (eccentricity and the longitude of the apogee) from three observations conducted near the planet’s opposition to the mean Sun on 25 October 1263, 9 December 1266, and 27 February 1273 (with longitudinal errors not exceeding 1/6°). He obtained an eccentricity of 3;15 (radius of orbit = 60), a value already encountered in Ptolemy’s Canobic Inscription, and a longitude of the apogee of 258;38° in 1273. A calculational mistake prevented him from measuring the more accurate value of 3;23 for the eccentricity; nevertheless, his apogee longitude stands as the most precise determination in the Islamic astronomical tradition. The accuracy of his values for the Ptolemaic parameters of Saturn and the quantitative outcomes of his theory are examined comprehensively and comparatively with all other known theories established in the late Islamic period, especially Saturn’s theory laid out in the Īlkhānī zīj. As a technical case study, this investigation furnishes new insights into the nature of observational practice and theoretical innovation in the medieval Islamic period.