Studies in Medieval Astronomy and Optics

In this selection of studies, J.L. Mancha explores aspects of the development of medieval optics and astronomy, including some medieval antecedents of the work of early modern astronomers. The articles deal with Latin, Hebrew and Arabic texts, and the process of translation and transmission of knowledge, and focus on three main themes. First, the theory and astronomical use of the pinhole camera in the 12th and 13th centuries; the texts edited here contain a solution to the problem of the formation of images cast by light through triangular apertures, equivalent to Kepler's, a description of the correct procedure for measuring solar apparent diameters using finite apertures, and a derivation of the Sun's eccentricity from its apparent diameters at apogee and perigee. Second, the characteristics of the Latin and Provençal versions of Levi ben Gerson's astronomical work, composed in collaboration with the author, as well as his tables and canons for finding syzygies and the mathematical methods used in the derivation of parameters. Third, different aspects of the survival of homocentric astronomy in the Middle Ages, especially al-Bitruji's model for trepidation and the technique for calculating the hippopede resulting from Eudoxan couples.

Professor J.L. Mancha directs a research unit in the History and Philosophy of the Physical and Mathematical Sciences at the University of Seville, Spain.

Contents: Preface. Astronomy and Optics: Egidius of Baisiu's theory of pinhole images; Astronomical use of pinhole images in William of Saint-Cloud's Almanach planetarum (1292). The astronomy of Levi Ben Gerson: The Latin translation of Levi ben Gerson's astronomy; Levi ben Gerson's astronomical work: chronology and Christian context; Heuristic reasoning: approximation procedures in Levi ben Gerson's astronomy; The Provençal version of Levi ben Gerson's table for eclipses; Right ascensions and hippopedes: homocentric models in Levi ben Gerson's astronomy, I: first anomaly. Arabic Astronomy in Western Texts: Ibn al-Haytham's homocentric epicycles in Latin astronomical texts of the 14th and 15th centuries; On Ibn al-Kammad's table for trepidation; A note on Copernicus' 'correction' of Ptolemy's mean synodic month; Al-Bitruji's theory of the motions of the fixed stars. Addenda et corrigenda; Index.