From: Thomas Hockey et al. (eds.). The Biographical Encyclopedia of Astronomers, Springer Reference. New York: Springer, 2007, pp. 1255-1256
Zacut: Abraham ben Samuel Zacut
Cirilo Flórez Miguel
Born Salamanca, (Spain), probably 1452
Died Damascus, (Syria), probably 1515
Abraham Zacut was an important Jewish astronomer who contributed to observational astronomy, astronomical tables, and our historical knowledge of astronomy in Spain. Zacut came from a family originally from France; however, the evidence indicates that he was born in Salamanca, and spent his early years there as a pupil of Isaac Aboab, from whom he received the extensive knowledge that would later make him famous. Although professionally a doctor, Zacut's fame came from his works in astronomy.
During his lifetime, Zacut maintained relationships with several notable figures, including Don Juan de Zúñiga, the last Master of the Order of Alcántara (Maestre de la Orden de Alcántara), and the Bishop of Salamanca, Gonzalo de Vivero, to whom he dedicated his most famous astronomical work. When Bishop Vivero died in 1480, Zacut lost his protector in Salamanca and moved to the court of Don Juan de Zúñiga for whom he produced the following works: Tratado breve de las influencias del cielo (Short treatise on the influence of the heavens) and De los eclipses del sol y la luna (On solar and lunar eclipses). We know that Zacut was in Lisbon on 9 June 1493, working for Juan II of Portugal. It is logical to assume that he moved to this city when the Jews were expelled from Spain following the order of the Catholic kings in 1492. Zacut also worked for the brother of King Manuel I, who is said to have sought Zacut's advice for Vasco de Gama's trip around Africa, for which Zacut gave a favorable opinion. When in 1496 King Don Manuel ordered the Jews expelled from Portugal, Zacut fled Portugal and moved to Tunisia, where he was welcomed by a large Jewish colony. He lived in Carthage for several months, giving lessons in subjects for which his expertise was renowned. He eventually moved to the Ottoman lands and died, probably in 1515 although a death date of 1522 has also been suggested.
It is not clear whether or not Zacut taught at the University of Salamanca. However, he was in contact with and influenced some of the professors of astrology there. For example, Juan de Salaya, who was a professor of astrology from 1464 to 1469, translated Zacut's work titled La Compilación Magna (ha‐Hibbur ha‐gadol or The magnus compilation) from Hebrew into Spanish. The Latin translation, known as Almanach Perpetuum, was made by José Vizinho and first published in Leira in 1496. It became essential for the development of Spanish and Portuguese navigation at the end of the 15th century. The Spanish translation made Zacut famous due to its influence on his contemporaries.
La Compilación Magna was commissioned by Zacut's protector, Gonzalo de Vivero. Indeed the bishop left instructions regarding Zacut in his will as follows:
…to deliver to the Jew Abraham, astrologist, five hundred maravedises and ten measures of grain, and instructed that certain works which were in Romance, written by the mentioned Jew, should all be published in a volume together with his other books in his [i. e. the bishop's] church, because it is worthy to understand the tables made by the mentioned Jew.
This volume could be Incunable 176, presently kept at the Salamanca University Library, which contains the Spanish translation of La Compilación Magna that was dictated by Zacut to the translator Juan de Salaya.
La Compilación Magna is a collection of astronomical tables with rules (canons) that served several purposes. The tables were calculated for the meridian of Salamanca for the radix year 1473. The first part of the collection contains the rules in 19 chapters, a number Zacut uses because he considers it a golden number, following the indication of Maimonides. In those chapters he first analyzes the positions of the Moon and the Sun, their movements, circumstances, and eclipses, and then moves to the astrological h