A treatise devoted to the solar and lunar motion. The title refers to Almagest IV.2, where Ptolemy describes the methods of his predecessors for establishing a lunar theory, although the main text does not include explicit references to Ptolemy. Full title: Qawl fī Iḍāḥ al-wajh alladhī dhakara Baṭlamyūs anna bi-hī staḫraja man taqaddama-hu masīrāt al-qamar al-dawriyya wa-hiya al-mustawiya.

Sezgin lists two different works by Thābit on the topics of Almagest IV. However, Morelon (esp. pp. lxxxii–lxxxiii) established that these are rather two versions of the same treatise. The present original and more coherent one is extant in Istanbul, Köprülü, Fazıl Ahmed Paşa 948 with the title mentioned above. This witness is of special importance as it was copied by Thābit’s great-grandson in 370/981. For a description of the second version, simply entitled Risāla fī Ḥarakat al-nayyirayn, see C.1.27.

Text: [ed. Morelon, Thābit ibn Qurra]

[Incipit] (p. 84) كلّ زمانين متساويين فإنّ كلّ واحد من النيّرين إنّما تستوي حركته الحقيقيّة فيهما على أحد أربعة أوجه فقط. [Explicit] (p. 92) فإذا قسمنا هذا المسير على عدد أيّام ذلك الزمان كان ما يخرج وهو مسير القمر المستوي في الطول في اليوم الواحد معلومًا.

Bibl.: Ibn Abī Uṣaybiʿa, ʿUyūn al-anbāʾ (ed. MüllerAugust Müller, ʿUyūn al-anbāʾ fī l-ṭabaqāt al-aṭibbāʾ li-ibn Abī Uṣaybiʿa, 2 vols, Cairo: al-Maṭbaʿa al-Wahbiyya, 1882, vol. I, p. 220); Ibn al-Qifṭī, Taʾrīkh al-ḥukamāʾ (ed. LippertJulius Lippert, Ibn al-Qifṭī’s Taʾrīḫ al-ḥukamā, Leipzig: Dieterich, 1903, p. 117). — SuterHeinrich Suter, Die Mathematiker und Astronomen der Araber und ihre Werke, Leipzig: Teubner, 1900, pp. 34–38; GAS VIFuat Sezgin, Geschichte des arabischen Schrifttums. Vol. VI: Astronomie bis ca. 430 H., Leiden: Brill, 1978, pp. 166 and 167. — E. Bessel-Hagen and O. Spies, ‘Ṯābit b. Qurra’s Abhandlung über einen halbregelmäßigen Vierzehnflächner’, Quellen und Studien zur Geschichte der Mathematik, Astronomie und Physik. Abteilung B: Studien 2 (1933), pp. 186–198, here pp. 187–189; Régis Morelon, Thābit ibn Qurra. Œuvres d’astronomie, Paris: Les Belles Lettres, 1987, pp. lxxx–xcii, 83–92, and 222–229; Régis Morelon, ‘Tābit b. Qurra and Arab Astronomy in the 9th Century’, Arabic Sciences and Philosophy 4 (1994), pp. 111–139, here pp. 115–118 (reprinted in Régis Morelon, ‘The Astronomy of Thābit ibn Qurra’, in Roshdi Rashed (ed.), Thābit ibn Qurra. Science and Philosophy in Ninth-Century Baghdad, Berlin / New York: de Gruyter, 2009, pp. 601–618); Fuat Sezgin, Thābit Ibn Qurra ibn Zahrūn al-Ḥarrānī (d. 288/901). Three Treatises on Mathematics and Astronomy. Reproduced from MS Köprülü 948, Istanbul, Frankfurt am Main: Institut für Geschichte der Arabisch-Islamischen Wissenschaften, 2011; Pouyan Rezvani, Si risāla az Thābit ibn Qurra (Sāʿat-hā-yi āftābī, Ḥarikat-i khurshīd wa māh, Chahārdah wajhī-yi muḥāt dar kura). Nuskha bargardān bi qatʿ-i aṣl-i nuskha-yi khaṭṭī-yi bi shumāra-yi 948, Kitābkhāna-yi Kūprūlū (Istānbūl), kitābat-i 370 H., Tehran: Miras-e Maktoob, 2014.

Ed.: Edition and French translation by Morelon (Thābit ibn Qurra, pp. 83–92). German translation of the introduction in Bessel-Hagen & Spies (p. 188). In addition, facsimile editions of Istanbul, Köprülü, Fazıl Ahmed Paşa 948 were published in Sezgin, Thābit and in Rezvani.