Galileo Galilei was an Italian astronomer, physicist and engineer, but also an astrologer. It was only recently that his astrological practices came to light, when his astrological ‘Manuscript 81’, entitled “Astrologia nonnulla”, got published in 2016 and is now part of his Collected Works. It contains horoscopes of 19 people in Galileo’s own hand, mostly patrons, students and family members; he was obviously seeking to raise some extra money, as we can see in the entries to his accounting books.
Other evidence of his astrological practices include his first investigation by the Venetian Inquisition in 1604, being accused of practicing deterministic astrology (a heresy, as only God knows what is going to come) but he could convince the Inquisition that he was only pointing out and interpreting personal traits of his clients (the Church did not seem to have objected to that), and the case was dropped.
This position follows closely the arguments of St. Thomas Aquinas, and we may even surmise he used it for his defense. Aquinas acknowledged that heavenly bodies have some influence over the physical world, which could be observed in natural phenomena like weather patterns and the ripening of plants. However, he firmly rejected the notion that the stars could determine human free will or moral actions.
‘Le opere di Galileo Galilei - Testi, Appendice - vol. III’
Galileo facing the Inquisition
St.Thomas Aquinas (died 1274)