Hi nico, going to throw my tuppence worth in, because I've gone off and on astrology over the years as well.
It does bother me a bit, I must admit, but carry on paying attention to astrology because it seems to "work", when done properly and in enough detail.
It seems like a lot of the explanation of how it works is justification after the fact ...
I think we can postulate with a high level of confidence that the beginnings of astrology were based on the idea that the stars DID have some sort of relation - either influential or descriptive/predictive - with life on earth (not just humans, but with the agricultural cycle as well). To dismiss that because astronomical forces are negligible kind of misses the point, in my opinion, because the early practitioners of astrology wouldn't know from gravitational, weak, strong, electromagnetic forces ... huh? The stars were seen as heavenly bodies, perhaps angelic even, that had a spiritual connection of some sort. Maybe they still do, who knows, but that's not the kind of thing we could ever measure with an instrument.
So I think it's a little bit disingenuous to say that none of that really matters, it's all symbolic, it's the houses/signs, not the constellations stupid ... because originally it was the constellations.
But I suppose it could be similar to the way high magic evolved from "low" or "cunning" magic. The original soothsayers would have made some sort of correlation between their own astronomical observations and events or personalities, and then the astrologers got hold of the concept and added the bells and whistles - rising signs, conjunctions, houses, all that stuff that makes modern astrology so intricate and satisfying to the mystical geek in us.
I don't guess that answers any of your questions, but just some thoughts this thread has sparked off.
yr pal, Fox
"So good luck came, and on my roof did light, like noiseless snow."
– Robert Herrick, from 'The Coming of Good Luck'