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Avraam Zacuto - biography

Abraham Zacuto (Hebrew: אברהם זכות‎, Portuguese: Abraão ben Samuel Zacuto, also Abraham ben Samuel Zacut and Abraham Zacut) (August 12, 1452 – probably 1515) was a Sephardi Jewish astronomer, astrologer, mathematician and historian who served as Royal Astronomer in the 15th century to King John II of Portugal. The crater Zagut on the Moon is named after him.


Zacuto was born in Salamanca, Spain in 1452. He may have studied and taught astronomy at the University of Salamanca. He later was for a time teacher of astronomy at the universities of Zaragoza and then Cartagena. He was versed in Jewish Law, and was rabbi of his community.

With the general expulsion of the Jews from Spain in 1492, Zacuto took refuge in Lisbon, Portugal. Already famous in academic circles, he was invited to court and nominated Royal Astronomer and Historian by King João II, a position which he held until the early reign of Manuel I. He was consulted by the King on the possibility of a sea route to India, a project which he supported and encouraged. Zacuto would be one of the few who managed to flee Portugal during the forced conversions and prohibitions of departure that Manuel I enacted, in order to keep the Jews in Portugal as nominal Christians for foreign policy reasons (see History of the Jews in Portugal). He fled first to Tunis, and later moved to Jerusalem. He died probably in 1515 in Jersusalem, however, other reports indicate his death to occur in Damascus and the death to occur in 1520.


Zacuto perfected a metal version of astrolabe, making it an instrument of more precision. He also wrote a highly accurate for the time astronomical table (Almanach Perpetuum) which were used by Portuguese ship captains to determine the position of their caravels in high seas through calculations on data acquired with the astrolabe. His contributions were valuable for the Portuguese seamen allowing them to reach Brazil and India in safe.

The book was written while he was in Spain in Hebrew, with the title Ha-jibbur Ha-gadol. He published it in a printing press of Leiria in 1496. Being a property of Abraão de Ortas, the book Biur Luhoth, or in Latin Almanach Perpetuum, was soon translated into Latin and Spanish. The astronomical tables (ephemerides) for the years 1497 to 1500 were (in conjunction with the new metal astrolabe) instrumental to the Vasco da Gama and Pedro Álvares Cabral exploring voyages to India and Brazil respectively.

In 1504, while in Tunisia, he wrote a history of the Jewish people, Sefer Hayuhasin, since the Creation of the World until 1500, and several other astronomical/astrological treatises. The History was greatly respected and was reprinted in Cracow in 1581, at Amsterdam in 1717, and at Königsberg in 1857, while a complete edition was published by Filipowski in London at 1857. Annotations in Hebrew to chapter five of "Sefer Hayuhasin", were published by Yoel Lieberman in 2001 in a masters thesis called "A Record of Medieval Sages In Sefer Yuchasin of Rabbi Abraham Zacut". The book is available in the Jewish National and University Library in Jerusalem. It was translated into English in 2005 containing notes by Professor Thomas Glick of Boston University with a short historical sketch of Zacutoas titled "The Book of Lineage". The translation was published by the Zacuto foundation founded by Dr. Vladimir Rozenblit, a 20th generation direct descendant of Zacuto.

Publications by Zacuto

  • 1478, ha-Hibbur ha-gadol (La Compilación Magna), his first astronomical book, translated into Castilian 1481 by himself and Juan de Salaya from the University of Salamanca. In 1496 the work was translated into Latin translation by José Vizinho and published in Leira as Almanach Perpetuum or Tabule tabularum celestium motuum astronomi zacuti. This work became important for the contemporary explorers.
  • 1486, Tratado breve en las ynfluencias del cielo, and De los eclipses del sol y la luna.
  • 1498, Sefer haYuhasin, historical text for the Jewish people.
  • 1498, astrological text predicting that the messias would come in 1503/4.

after 1498, Mishpetei ha-'istagnin (Judgments of the astrologer)

Article author: Zipora Galitski
Article tags: biography
The article is about these people:   Avraam Zechut (Zakuto)

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