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Abraham Zacuto (Hebrew: אברהם זכות‎, Portuguese: Abraão ben Samuel Zacuto, also Abraham ben Samuel Zacut and Abraham Zacut) (1452 – probably 1515) was a Sephardi Jew 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.[1] 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.[2] 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.[1] He died probably in 1515 in Jersusalem, however, other reports indicate his death to occur in Damascus and the death to occur in 1520.[1]


page from Almanach Perpetuum.

Zacuto perfected the astrolabe, which only then became an instrument of precision, and he was the author of the highly accurate Almanach Perpetuum that were used by ship captains to determine the position of their Portuguese caravels in high seas, through calculations on data acquired with an astrolabe. His contributions were undoubtedly valuable in saving the lives of Portuguese seamen, and allowing them to reach Brazil and India.

While in Spain he wrote an exceptional treatise on astronomy/astrology in Hebrew, with the title Ha-jibbur Ha-gadol. He published in the printing press of Leiria in 1496, property of Abraão de Ortas the book Biur Luhoth, or in Latin Almanach Perpetuum, which was soon translated into Latin and Spanish. In this book were the astronomical tables (ephemerides) for the years 1497 to 1500, which were instrumental, together with the new astrolabe made of metal and not wood as before, to Vasco da Gama and Pedro Álvares Cabral in their 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 in 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". It is available in the Jewish National and University Library in Jerusalem. Sefer Hayuhasin was translated into English in 2005 by Israel Shamir see [1].The English translation contains notes by Professor Thomas Glick of Boston University, and is called "The Book of Lineage". The translation was published by the Zacuto foundation founded by Dr. Vladimir Rozenblit, a 20th generation direct descendant of Zacuto, and headed by Israel Shamir. The book (in English) also contains a short historical sketch of Zacuto.

Publications by Zacuto[1]

  • 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.[3]
  • 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)


  1. ^ a b c d Chabas J, Goldstein BR. Abraham Zacut:Supplemental Note for a Biography. p. 6–11. ISBN 0871699028.  
  2. ^ J. Bensaude (1912): L'astronomie antique au Portugal á l'épogue des grandes découvertes, pp. 6, 18-29
  3. ^ Miguel CF. "Zacut: Abraham Ben Samuel Zacut". Retrieved 2009-06-15.  

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