Guido Bonatti

Guido Bonatti (died between 1296 and 1300) was an Italian mathematician, astronomer and astrologer, who was the most celebrated astrologer of the 13th century. Bonatti was advisor of Frederick II, Holy Roman Emperor, Ezzelino da Romano III, Guido Novello da Polenta and Guido I da Montefeltro. He also served the communal governments of Florence, Siena and Forlì. His employers were all Ghibellines (supporters of the Holy Roman Emperor), who were in conflict with the Guelphs (supporters of the Pope), and all were excommunicated at some time or another. Bonatti's astrological reputation was also criticised in Dante's ''Divine Comedy'', where he is depicted as residing in hell as punishment for his astrology.

His most famous work was his ''Liber Astronomiae'' or 'Book of Astronomy', written around 1277. This remained a classic astrology textbook for two centuries. Provided by Wikipedia