In antiquity the words astronomy and astrology had been synonymous; in the first Christian centuries spread the distinction between astronomy, the science of stars, and astrology, the art of divination by the stars. Basically, Christianity taught the omnipotence of their Creator against the omnipotence of the stars and opposed the freedom of the will against the determinism of astrology. But within these limits the astrological worldview was generally accepted.

Even if various Christian councils condemned astrology, the belief in the worldview it implies didn’t suffer a serious damage.... We can find, in the late European Middle Ages, a number of universities teaching astrological matters.


A very nice site about Astrology and the Middle Ages:
The heavens are telling the glory of God