Over New Years, my sister accused myself and another sister of being "close-minded" for not believing in astrology. It stood out to me that defining "close-minded" as "not believing in something" is pretty crazy. For one thing, nobody believes in everything so the accusation is hypocritical. Secondly, beliefs usually (if not always) imply disbeliefs. If you believe it to be cold outside, that means you don't believe it to be hot. But thirdly, I disagree with the commonly implied association between "open-mindedness" and belief.
Being open- or close-minded is one thing. Believing or not believing is a completely separate thing. I'm not sure open-mindedness is even correlated with belief.
I think there are some statements that are so clearly false that it requires close-mindedness to continue to believe them. In the case of astrology, an open-minded person would consider the available evidence, come up with arguments for why astrology is likely true or false, and search for a model of the world where it's being true makes sense. Given that there is nothing approaching good evidence, good reasoning, or a model of the world where astrology makes sense, in order to still believe that astrology is true, you need to be actively closing your mind to the alternative possibility. I think an open-minded person would struggle to believe in astrology because they would be open to impartially weighing the evidence and various arguments to figure out what's really true. An open-minded consideration such as this can only lead to the conclusion that astrology is false.