José Vizinho, (also known in English as Joseph Vecinho), was a Portuguese Jew, born in the town of Covilhã, court physician and scientist at the end of the fifteenth century. He was a pupil of Abraham Zacuto, with whom he studied mathematics and cosmography, and was regarded as an authority on the subject by king John II of Portugal. He was sent by the king to the Gulf of Guinea in 1483, to measure the altitude of the sun, using an astrolabe improved by Jacob ben Machir. This was one of several voyages that resulted in the production of detailed maps of areas of the eastern Atlantic that had been unknown to Europeans until then.