John Dee was an astrologer, a mathematician and a scientist. He cast horoscopes for Queen Mary I, but when he made the mistake of befriending Queen Mary’s younger sister, Elizabeth, he was tried for trying to kill Mary with black magic. He was acquitted, but after he was released, Mary did die.
When Elizabeth I became Queen she asked him to choose an auspicious date for her coronation, and made him her court astrologer.
We have one record of Dee’s success as an astrologer – his horoscope for Sir Philip Sidney, which runs to 62 pages with several predictions. Dee predicted that Sidney would have a wonderful career between the ages of 15 and 31, but at that time he would be in mortal danger from a sword or gunshot wound. If he survived this, he would bring greater glory to himself. Sir Philip Sidney was killed on 17th October 1586, aged 31.  
Dee spent much of his later life attempting to summon angels to learn the secrets of creation from them, with the assistance of a scryer, while advising naval expeditions with his extensive knowledge of geography and cartography.
While Dee was a devout Christian, his faith and religion were extremely heterodox. His works on alchemy, astrology, and mathematics have become popular among occult circles, while his angel diaries were compiled as John Dee's Books of Mystery.
- Propaedeumata Aphoristica, 1558.
- Monas Hieroglyphica, 1564.
- Mathematical Preface to Euclid, 1570.
- John Dee's Five Books of Mystery (compiled posthumously)
- Deborah E. Harkness, John Dee's Conversations with Angels : Cabala, Alchemy, and the End of Nature