Project icon: lavishly furnished initial letter with a painting of Ptolemy using an astrolab.

Ptolemaeus Arabus et Latinus

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Work B.17

Liber proiectionis radiorum stellarum


‘(ed. Venice 1484) Scientia proiectionis radiorum. Cum proiectionem radiorum stellarum scire volueris, scias gradus ascendentis et super eum 4 angulos — et si sint gradum anguli terre et gradum ascendentis fuerit, eum prime superaddes, et quod collectum fuerit erit locus radiationis equate.’


A short text on the projection of rays.


In most manuscripts and in the three early printed editions, this text is appended to, or considered part of, the Quadripartitum in the translation of Plato of Tivoli. In MS Oxford, BL, Savile 17, the text occurs as the last chapter of Alcabitius’s Introductorius. Contrary to Lemay’s opinion (Abū Ma‘šar al-Balḫī [Albumasar]: Liber introductorii maioris ad scientiam judiciorum astrorum, Napoli, 1995-1996, IV, 56), this text is not taken from Albumasar, Introductorius maius, VII.7 (‘Differentia VII in proiectione radiorum planetarum secundum opus Tholomei’), with which it shares only the subject-matter (but not the wording) of its first paragraph.


F. J. Carmody, Arabic Astronomical and Astrological Sciences in Latin Translation. A Critical Bibliography, Berkeley-Los Angeles, 1956, 21 (nos. 43-44).