I think it's easy to respond negatively to astrology as quackery, pseudo-science, and con-artistry. I think it's helpful here to try to get some distance from that, and think of it as a religion, much like any other.
Astrology is based on traditional mythological elements, much of it with a great deal of history, stories told long ago, etc. I think it's pretty clear that stuff is on topic. Myths involving Capricorn, for instance, is clearly on topic in my book.
I think it's also clear this isn't the place for a practicing astrologer to seek advice on their craft, in the same way that it isn't the place for a practicing Christian to seek moral guidance.
Which brings us to the more recent question How is the “power” of an astrological aspect computed?. That falls into a bit of a gray area, but I'm kinda inclined to call it on topic. Looking at the question there:
what are the different ways to compute the power, when did they arise and what, if any, reason is given?
If we take astrology to be a religious or mythic system, then asking about the mythological basis and history for an element of that system seems to be reasonably topical to me. The question is being asked here, on Mythology.SE, not on Pseudoscientific-Bologna.SE. It is implied that it is asking for the mythology, rather than for some poorly-reasoned scientific-sounding justification for the practice.
So, I don't believe it is off topic. That said, I have no interest whatsoever in that question and no intention of looking into it. I suspect I may not be the only one who feels that way about it.