Why are there astrological signs in some churches and abbeys?

There are Christian churches and abbeys including very old ones in Hungary where we can find frescos about astrological signs. These frescos are relative new, probably a few hundred years old. As far as I know Christianty and astrology are mutually exclusive, so I wonder how these frescos were accepted. I guess this is not restricted to Hungary, but maybe it is something relative common. Is there any archeological or historical explanation about this?