Note 415 — APPENDIX D.

Abraham ben Samuel Zacuto was professor of astronomy and mathematics in the University of Salamanca when King John II called him to Portugal in 1492, and appointed him Astronomer Royal. He is the author of Ephemerides, originally written in Hebrew, a Latin translation of which, by José Vizinho, one of his pupils, was first printed in 1496—on the eve of Vasco da Gama’s departure—although there can be no doubt that these useful tables previously circulated in MS. José Vizinho is perhaps identical with the physician José whom King John had charged, jointly with Master Rodrigo, to prepare tables of the declination of the sun, which would enable navigators to determine their latitude after they had lost sight of the Pole star. Rudolf Wolf (Geschichte der Astronomie, p. 97) credits Regiomontanus with having produced the first set of “practical” tables for the use of mariners. He does not even once mention Zacuto in his history, and states that the tables of the great German astronomer were those made use of by Dias and Vasco da Gama. As the Ephemerides of Regiomontanus were printed in 1474, they naturally became more widely known than those of Zacuto, which only circulated in MS., and they were, perhaps, brought to Portugal by Martin Behaim. It cannot, however, be doubted that the tables which Vasco da Gama took with him were those of Zacuto.

For the contents of the first printed edition of Zacuto’s Almanach Perpetuum, see Antonio Ribeiro dos Santos in Memorias de Litteratura Portugueza, 2 edição, VIII, p. 46; for later reprints of the Tables of the Declination of the Sun, see Luciano Cordeira in the Boletim of the Lisbon Geographical Society, 1883, p. 163.