ר׳ אברהם זכות

ר׳ אברהם בן שמואל זכות (1452–c.1515) was a Sephardi astronomer, mathematician, historian and rabbinic scholar whose tables helped transform practical navigation. Born in Salamanca, he studied Jewish learning within his family and under ר׳ יצחק אבוהב while mastering mathematical astronomy. In the 1470s he composed החיבור הגדול, a Hebrew astronomical handbook with tables calculated for Salamanca. ר׳ יוסף ויזיניו translated and adapted these into Latin and Castilian as the Almanach Perpetuum, printed at Leiria in 1496 and used by Portuguese navigators. After the 1492 Spanish expulsion, ר׳ אברהם entered Portugal, where King John II and then Manuel I employed his astronomical expertise. Portugal’s forced-conversion policy drove him into a second exile in 1496–97. He eventually reached Tunis, where in 1504 he completed ספר יוחסין, a chronology of Jewish tradition and rabbinic transmission that also preserves valuable historical notices. His final itinerary is imperfectly documented; leading modern authority records place his death probably in Damascus around 1515, while traditions also connect his last years with Jerusalem. His career links the final flowering of Iberian Jewish science, the age of Atlantic navigation and the post-expulsion reconstruction of Sephardi intellectual life.