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The linear astrolabe was invented by Sharaf al-Dīn al-Ṭūsī (fl. c. 1180) and although several Arabic monographs on the subject have reached us, none have received sufficient scholarly attention. As a result, one of the most important features of Ṭūsī’s invention, the gnomonic application, remains unknown. Based on an analysis of all known monographs on the linear astrolabe, this paper will discuss the gnomonic application of the linear astrolabe, which is an alternative to the azimuth lines typical of the plane astrolabe. We will also consider the potential role of Ṭūsī’s pupil, Kamāl al-Dīn ibn Yūnus (d. 1242), in the improvement of this instrument. Finally, after surveying the available manuscript copies of the above-mentioned monographs, we present a full edition and translation of one such text and an edition and translation of one chapter, on the gnomonic application, from another text.

Autolycus’ On the Moving Sphere is among the earliest Greek mathematical works to reach us and was considered a staple of the middle books, to be studied between the Elements and the Almagest. This was among the many mathematical works translated to Arabic in the 3rd/9th century and it was the subject of several translations, redactions, and recensions. Analyzing the available copies of al-Kura al-mutaḥarrika, five different versions were identified. In this paper, we analyze these five versions, with a focus on the seventh proposition, in order to characterize their relations to each other and to the extant Greek text.