A text on the construction of the universal astrolabe in six chapters. According to the colophon, it was translated from the Arabic in London in ‘era 1185’, i.e. in 1147 A.D., and three of the four complete manuscripts name Robert of Chester (‘Robertus Cestrensis/Castrensis’) as the translator (MSS Cambridge, GCC, 35 (141); Fermo, BC, 85; and Vienna, ÖNB, 5311). The text is unambiguously attributed to Ptolemy not only in the colophon, but also in the body of the text, where the author refers to the Almagest as his own work (‘librum meum Almagesti perlegat’, c. 6, Oxford, BL, Digby 40, f. 7r). Kunitzsch, 490, argued that this work is not a translation, but a Latin compilation that borrows certain technical terms from previous works on the astrolabe. The possibility remains, however, that the translator was familiar with earlier Latin works on the subject. Robert of Chester (‘Robertus Cestrensis’) is also credited with a text on the use of the astrolabe in 35 chapters (De officio astrolabii) extant in MSS Milan, BA, H. 109 sup., s. XV, f. 9v-17v, and Oxford, BL, Canon. Misc. 61, f. 12r-22v (see), on which see Kunitzsch, 492 (also 506), and Nothaft, 194.

Note The text once occurred in MS Berlin, SBPK, lat. qu. 510 (s. XIII¹) as shown by the medieval table of contents of this manuscript: ‘De compositione astrolabii universalis Ptholomei’ (see MS entry under Note).

Text ‘(Oxford, BL, Digby 40) In nomine domini pii et misericordis incipit liber de compositione universalis astrolabii. [translator’s preface] Ptolomeus igitur, Mercurii incedens vestigiis in libro suo qui vocatur Almagesti, de motu sic ait: Ait enim omnis motus aut de puncto aut ad punctum — (1v) a docto artifice perpenditur. Explicit prologus. Incipit liber. [text] Sit igitur mater tabula, astrolabii videlicet generalis ex eramine rotundissime composita — cum una eademque utrique conveniat ad plenum dicetur. Explicit liber Ptolomei de compositione astrolabii universalis quem scilicet <Robertus Cestrensis> in civitate Londonie ex Arabico in Latinum transtulit, era millesima centesima LXXXV.’

Bibl. M. Steinschneider, ‘Zum Speculum astronomicum des Albertus Magnus, über die darin angeführten Schriftsteller und Schriften’, Zeitschrift für Mathematik und Physik 12 (1867), 357-396: 393; C. H. Haskins, Studies in the History of Mediaeval Science, Cambridge, 1927 (2^nd ed.), 122; F. J. Carmody, Arabic Astronomical and Astrological Sciences in Latin Translation. A Critical Bibliography, Berkeley-Los Angeles, 1956, 19 (no. 19, also no. 17); J. D. North, Richard of Wallingford: An Edition of His Writings with Introduction, English Translation and Commentary, Oxford, 1976, III, 162-164; P. Kunitzsch, Glossar der arabischen Fachausdrücke in der mittelalterlichen europäischen Astrolabliteratur, Göttingen, 1983 (Nachrichten der Akademie der Wissenschaften in Göttingen, I: Philologisch-Historische Klasse 11 (1982), 459-571), 489-491; C. P. E. Nothaft, Graeco-Arabic Astronomy for Twelfth-Century Latin Readers. Ptolomeus et multi sapientum (Abraham Ibn Ezra) – Robert of Chester, Liber canonum, pt. II, Leiden-Boston, 2023, 193-194. For works on the astrolabe attributed to Ptolemy in Arabic (and Hebrew), see M. Steinschneider, Die hebraeischen Uebersetzungen des Mittelalters und die Juden als Dolmetscher. Ein Beitrag zur Literaturgeschichte des Mittelalters, Berlin, 1893, II, 536-538; F. Sezgin, Geschichte des arabischen Schrifttums, V: Mathematik, Leiden, 1974, 171-174 (nos 2-3), and VI: Astronomie, Leiden, 1978, 95 (no. IV); and H. Y. Sheynin, ‘Claudius Ptolemy? Pseudo-Ptolemy? The Main Source of Moses Almosnimo’s Treatise on Astrolabe’, Journal for the History of Astronomy 46 (2015), 343-350.

Modern ed. ---