Abraham Zacut (1452-1515) of Salamanca was an outstanding intellectual figure in the Spanish Jewish community on the eve of the expulsion in 1492. His scientific work began in the 1470s, & continued in exile, in Portugal, N. Africa, & ultimately in Jerusalem. This monograph focuses on some of his important contributions to astronomy, namely, those that appear in the book published in Leiria, Portugal, in 1496, generally known as the “Almanach Perpetuum”; this publication is to be distinguished from “ha-Hibbur ha-gadol” (“The Great Composition”) that Zacut composed in Hebrew in 1478. Indeed, one of the findings in the course of research for this vol. is that these are distinct works. Bibliography. Charts & tables.