This previously unnoticed translation of the Planispherium is said to have been ‘corrected and rectified’ by one master Isaac Hebreus (‘magister Hisaac Hebreus’), but it really is a new translation, distinct from Hermann of Carinthia’s (A.6.1). It is extant in a unique copy dated 1518, which, judging from the corrections, is probably the autograph. The text ultimately derives from the Arabic version edited by Maslama al-Majrīṭī’s, for it includes Maslama’s added material (see A.6.1), here attributed to ‘Mesulam’ (e.g., f. 81v, 82v and 83r) or to ‘Abo Alcasis Mesulam filii Alchamad’ (Extra Chapter f. 84v-85r), but it appears to have been translated from a Hebrew intermediary. This is already suggested by the name of the translator and by the nature of the manuscript, which mixes scientific texts in Latin and in Hebrew in a most unusual way. Moreover, the beginning and the end of the text fully match the Hebrew version as found in MS Modena, BEU, or. 27 (Alfa O.3.14), f. 116v-122r (my thanks to Niran Garshtein, who translated the relevant passages for me). This Hebrew version is generally believed to be a translation of Hermann of Carinthia’s Latin version (see M. Steinschneider, Die hebraeischen Uebersetzungen des Mittelalters und die Juden als Dolmetscher. Ein Beitrag zur Literaturgeschichte des Mittelalters, Berlin, 1893, II, 535-536; P. Kunitzsch, R. Lorch, Maslama’s Notes on Ptolemy’s Planisphaerium and Related Texts, München, 1994, 84; and R. Lorch, ‘Ptolemy and Maslama on the Transformation of Circles into Circles in Stereographic Projection’, Archive for History of Exact Sciences 49 (1995), 271-284: 276), but this question would perhaps deserve a fresh investigation. The translator ‘magister Hisaac Hebreus’ must be identified with the ‘magister Hysaach Hebreus Francigena’ who translated, also from Hebrew, Savasorda’s Liber de forma terrae et de figuratione corporum coelestium necnon de ordine motus stellarum (=Abraham bar Ḥiyya, Ṣurat ha-ʿareṣ, ‘The Form of the Earth’), whose unique copy (Vatican, BAV, Ott. lat. 2079, see also Note below) is in the same hand as the Demonstrationes astrolabii. The translation of Savasorda’s works provides us with some context for it is dedicated to ‘Albertus Pius de Sabaudia’, i.e., Alberto III Pio, Prince of Carpi (1475-1531), a patron of humanists and dedicatee of scientific works, including Hebrew-into-Latin translations. This matches the context of the Demonstrationes astrolabii, not only the date (1518), but also the fact that the manuscript was copied in northern Italy, perhaps in Mantua, about 50 kilometers north of Alberto Pio’s castel in Carpi.

Note The translation of Savasorda’s Liber de forma terrae et de figuratione corporum coelestium necnon de ordine motus stellarum (‘Liber de forma terrae et de figuratione corporum coelestium necnon de ordine motus stellarum. Dixit Abraam patriarcha filius Rabi Chagia Hispani: Scientia astrorum iuxta hominum opinionem in duas maximas dividitur partes — et precepta ipsius legis omnibus diebus nostris. Amen. Expletus est hic perutilis ac preciosus tractatus de astrologia quem traduxit ex Hebreo in Latinum magister Hysaach Hebreus Francigena ad complascentiam magnanimi ac sapientissimi principis domini Alberti Pii de Sabaudia. Laus Deo’, MS Vatican, BAV, Ott. lat. 2079, f. 1r-51v) has been briefly discussed by M. Steinschneider, ‘Abraham Judaeus – Savasorda und Ibn Esra. Zur Geschichte der mathematischen Wissenschaften im 12. Jahrhundert’, Zeitschrift für Mathematik und Physik 12 (1867), 1-44: 12 (reprinted in M. Steinschneider, Gesammelte Schriften, I, Berlin, 1925, 327-387: 342-343), and by J. M. Millàs Vallicrosa, La obra Forma de la Tierra de R. Abraham bar Ḥiyya Ha-Bargeloní, Madrid-Barcelona, 1956, 19-20, but the faulty reading ‘Alberti Sii’ (instead of ‘Alberti Pii’) in the colophon prevented these scholars from identifying the dedicatee. The colophon was correctly transcribed by G. Mercati, Codici latini Pico Grimani Pio e di altra biblioteca ignota del secolo XVI esistenti nell’Ottoboniana e I codici greci Pio di Modena, Città del Vaticano, 1938, 48-49, who identified Alberto Pio as the dedicatee and drew attention to another translation in the same hand (i.e., Isaac Hebreus's), namely Levi ben Gerson’s Liber sillogismi recti, in MS Vatican, BAV, Ott. lat. 1906, a manuscript which Mercati believes to have belonged to Alberto Pio. On Alberto Pio, see C. B. Schmitt, ‘Alberto Pio and the Aristotelian Studies of His Time’, in Società, politica e cultura ai tempi di Alberto III Pio, Padua, 1981, 43-64 (reprinted in C. B. Schmitt, The Aristotelian Tradition and Renaissance Universities, London, 1984, VI), esp. 44-45 and 60.

Text ‘(Milan, BA, D. 114 inf.) Demonstrationes astrolabii a Ptholomeo editae, correctae et rectificatae per magistrum Hisaac Hebreum. [text] Scripsit Ptholomeus ad Sirum: Postquam possibile est ut circuli secantes sphaeram appareant in superficie plana — (84v) non oportet dividere circulos per singulos gradus, sed sufficit divider eos per 30 gradus. [maslama’s extra chapter] Sequens capitulum non est Ptolomei sed est Abo Alcasis Mesulam filii Alchamad. Dixit Ptolomeus: Docuit in hoc tractatu quomodo debeamus describere orizontem et paralellos eius, qui dicuntur almucantarat — arcus eque divident horizontem et omnes eius paralellos. Finis. כבודך ה' י"ט תשרי רע"ט לע"כ.’

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