Gerard of Cremona’s Latin translation of the Almagest and the revision of tables

Until the late 15th century, knowledge of Ptolemy’s Almagest in the Latin West was constituted by Gerard of Cremona’s translation from Arabic into Latin. The text of Gerard’s translation has been examined carefully and its dependence on two different Arabic versions is well studied. However, the tables of Gerard’s Latin Almagest have not been scrutinized, and the relation to their Arabic or Greek counterparts has not been examined. In this article, I will analyze the historical mathematical structure of tables in Gerard’s Latin Almagest translated from the Arabic in comparison to their Arabic and Greek precursors. While Gerard’s text has proved to be a faithful translation from Arabic templates, some of the tables will turn out to be different. Fundamental tables for, for example, the chord interpolation values, declination, and rising times appear to have been recomputed in order to match Ptolemy’s proofs and paradigm computations, which, in contrast, generally diverge in both Greek and Arabic tradition with the tables. It remains unclear if Gerard himself or someone in his company recalculated these tables and thus deliberately aimed to correct the ancient classic of astronomy. By a systematic analysis of these tables, I intend to provide a novel perspective on the medieval transmission and translation of knowledge, its cross-cultural exchange, and especially the practice of Gerard of Cremona and his collaborator(s).