David Kalonymos was an Italian Jewish court physician, astrologer/astronomer in Naples. Jewish astronomers of the time were expected to write horoscopes and make astrological predictions based on astronomical calculations. Astrology was widely considered to be a form of wisdom, akin to the mysticism of Kabbalah and the teachings of the Talmud. In 1564, David wrote two astrological treatises, one of which is on the conjunction of Saturn and Jupiter. He dedicated the work to King Ferdinand I of Naples in the hope of obtaining religious liberty for Jews in southern Italy. A horoscope for David’s son born on March 28, 1458 has been preserved in a book in the library of Parma.
In 1466 David translated from Latin into Hebrew an astronomical work of John of Gmünd describing an astronomical instrument invented in Vienna in 1417. He also wrote a philosophical treatise on the Destructio Destructiones of Averroes.
Both of David’s sons, Calo and Chaim, followed their father in the practice of astrology and other philosophical activities.