The Risala Dhat Al–Kursi Attributed to Ptolemy A Treatise on the Celestial Globe with Stand

This book deals with the Risala Dhat al-kursi, a 33-chapter Arabic treatise on the celestial globe with stand. The treatise is attributed to Ptolemy in some manuscripts, to the Ottoman scholar Akhawayn in others, but is anonymous in most. The book begins with a survey of references to Ptolemaic works in Greek and Arabic sources, presenting various works attributed to Ptolemy either preserved in the original Greek or in translation, or considered lost, including both authentic works and pseudepigrapha. Next follows a critical edition of the treatise Dhat al-kursi, based on eight of the twenty-three manuscripts studied. The edition is accompanied by an English translation and an extensive mathematical commentary on each chapter, enriched with explanatory figures. The comparison between this treatise and the Treatise on the Celestial Globe by Qusta ibn Luqa (d. ca 912 AD), presented in parallel with the commentary, shows that the former is based on the latter; thus the treatise Dhat al-kursi should be considered a Ptolemaic pseudepigraphon. A transcription of the Arabic text of the treatise by Qusta ibn Luqa based on three of the eighteen examined manuscripts is included, so that the reader may compare the two texts. Furthermore, in order to examine Akhawayn's association with the treatise, a bibliographical and historical investigation is conducted, which examines the full range of works attributed to Akhawayn. However, the truth about the authorship was probably lost, as the result of various rivalries in the late fifteenth century.