Abraham Zacut (1452-ca. 1515), a Spanish-Jewish astronomer, completed his perpetual astronomical almanac, ha-Hibbur ha-Gadol, in 1478. Recognized for the accuracy of the astronomical tables in the volume, editions were published in Latin and Castilian and manuscripts circulated in Spanish, Arabic and Ladino. It is also thought that Spanish and Portuguese explorers relied on Zacut’s tables, as well as the perfected astrolabe he designed, while on their historic voyages to India and the Americas. Zacut's tables were republished in the sixteenth and seventeenth centuries and they continued to be copied in manuscript form until at least the eighteenth century. The manuscript of Ha-Hibbur ha Gadol shown here was transcribed in the seventeenth century from one prepared in 1489.