Here is a comprehensive list of arguments debunking astrology being debunked. As you will see, most of the debunking is just clarification, because critics of astrology, though educated, usually do not feel in any way required to learn what it is they are criticising. Don't worry, all the actual problems of astrology will be mentioned as well. Each article deals with one general group of particular criticisms and explains how all of them in reality miss the mark.
Astrology is a scam
While it is true that a sizeable number of people who claim to be doing astrology do so dishonestly and for money or influence, it is no different from people pretending to be medical doctors for money. Just like the fake doctors do not invalidate actual medical doctors, fake astrologers do not invalidate actual astrologers, strictly logically speaking. There are of course objections to this comparison you are most likely thinking of right now, so let's address them. First of all, you can tell actual astrologers from fake ones, just like you can tell actual doctors from fake ones. Believe it or not, astrology has a logical method based on a long tradition. I know you're thinking that all charlatans would just say that, but in the case of astrology in particular (along with numerology and partially tarot) it is true, while virtually all other psychic disciplines or divination methods do not possess anywhere near that much empirical logic in how they are being conducted. Regardless if you believe that astrology produces measurable results or not, it does have clear terminology and methods of interpretation, which are codified and translatable into modern psychoanalytical terms and therefore identifiable. There are of course differences between the terminologies and methods of astrology and scientific psychology, but I'll address them in detail later.
A good example of popular criticism against fake astrology, that does not apply to actual astrology, is the well-known Barnum's or Forer's Effect - a sufficiently vague reading will lead to virtually anybody identifying with it. That is supposed to work both for personality description (obviously) and also for predictions (vaguely stated likely future events are bound to happen and be identified by the subject, or even realized through a self-fulfilling prophecy). I have personally reviewed what were the contents of the fake readings provided during several tests of this effect, and they were indeed vague, flattering and vacuous. Unlike actual astrological readings. Actual astrological reading reads much more like a psychological analysis or a strategic prognosis, not seeking to flatter (or scare), not judging good and bad or happy and sad, and using as un-vague terms as possible. In fact, all advanced scientific typologies are compatible with astrology and their proper use is encouraged. Actual astrologists do not even consider the likelihood of subject's identification with any statement in the reading, because the given positions of planets in a horoscope strictly dictate sets of possible and impossible conclusions. Once again, you may question the causality between a constellation and any alleged effect it is supposed to have, but the traditional empirical (albeit intuitively collected and interpreted) nature of astrology makes an actual astrological reading clearly distinguishable from a cynical con artist's attempt at milking astrology's popularity.
CONCLUSION: Real charlatans do not make real astrology and there are many absolutely honest astrologers, some of which, strangely enough, offer their services for free or next to nothing. Also, vague reading is not good astrology - actual astrology is designed to be the opposite of vague, just like any decent psychological, sociological or political inquiry or evaluation.
Astrology has been debunked
Now you may say, okay, but neither honesty nor tradition make astrology necessarily true or even logical in any way. If astrologers aren't deluding others on purpose, they may be deluding themselves unwittingly, seeing patterns where there are none. Typical theoretical and methodological gripes of sceptics involve superficial criticisms like "there is no known force exerted by planets strong enough to influence us in any meaningful way" or "signs stereotype people into just twelve types". In both these instances and many more, these easy criticisms are a bit too easy, overlooking completely that astrology is something else than what they are criticising, or assuming science understands nature more completely than it does. There once again may be people claiming all sorts of things about astrology, but critical look at the core method used by majority of astrologers shows that it is not necessary for planets to directly cause anything at all, just like a thermometer doesn't cause temperature, and that with employing all the instruments of astrological typology, the overall number of unique permutations of a complete horoscope ranges in the billions. These critical misses are then usually accompanied by anecdotal examples of especially inept astrologers or negative personal testimonies, finished with a vague reference to "all the research that already showed there is nothing to it".
I have once again reviewed plenty of research that supposedly already debunked astrology, and for someone who knows both methodology of scientific research and astrological practice, the whole of the research both for and against astrology done so far is simply ridiculous. On one side, there are astrologers trying to do science, but very badly, and on the other, there are biased sceptics disproving something that isn't astrology or focusing the research on beating a dead horse, showing only obvious personal problems like "people are gullible" and "psychics are mostly overconfident". There were also few cooperations between these two groups, but only combining the failings of both. The measures of efficacy of astrology in most of these tests I've seen included a) people identifying with their own reading, which was intentionally vague; b) astrologers matching how much they think that they can accuratelly guess people's star signs, or perform other tasks better than at the level of chance. Moreover, there are real examples of favourable tests for astrology that are maybe manipulated or at least questionable, which are blown out of proportion to boost the charlatan image of ALL astrologers, just as there are interesting real results showing there may be something to astrology, which are systematically downplayed in how they are being interpreted or perhaps intentionally overlooked. An example of the allegedly fake results would be the (in)famous Gauquelin Mars Effect experiment, where his results may have been just a false positive in a form of statistical artifact. Or not. Statistics, strangely enough, do involve plenty of interpretation.
But I have even seen a clear and undeniable success of an astrologer in a proper test - a sceptic show invited an astrologer and gave him 12 blind dates, times and places of birth with only sexes specified, if I remember correctly. He made 12 personality readings, which were given to the subjects, who were supposed to say to what extent the reading fits them. Clearly to test the aforementioned Barnum's/Forer's Effect. All the subjects were expectedly reporting over 70% accuracy, so they switched the reading for the last two subjects. Guess how many percent they both attributed to the readings' accuracy - under 30%. Them both. Only the two of them. Of course, you may say it may have been an accident, the sample was too small after all. I'll tell you a secret - most of the reasearches allegedly debunking astrology also had small samples and/or questionable statistics, but you would automatically believe them more, if you are a self-proclaimed sceptic. The majority of "sceptics" in comments to the video with this test certainly refused to believe the astrologer didn't fail. Talk about bias and cherry-picking. Even the three sceptical committees from three different countries replicating Gauquelin's research with a clear goal of debunking it had to resort to questionable statistical interpretations and waited years and years after completing their reviews to publish them, hardly for any other reason than hoping in vain to find a more definitive way to disprove the validity of the data. And if you want to actually see the most significant and recent development, google "Carlson Currey Astrology", it should be a critical review of a study published in Nature, that claimed to disprove astrology, but actually turns out to prove it. A little - its methodology was pretty shoddy and its intent clearly biased, as usual, but some data can be saved from the wreckage. If you understand statistics, that is - hatin' is easy, actual science is hard, patient work.
CONCLUSION: Critics of astrology often know too little about what they're trying to debunk and the majority of the tests of astrology so far have usually been too flawed in their methodology to show anything with any certainty.
Astrology is not a science
Now that I've dealt with some of what astrology isn't, even though it is accused of it - contradicting known facts and being sufficiently disproved - I have to address one more such thing: lacking theoretical explanation (and thus being invalidated). First of all, lack of theoretical explanation does not invalidate results in any way, even "magical" tool is still a useful tool if it has purpose and some measure of reliability, just like compass was for a very long time before it was explained by science. Secondly, for some time there has been a number of entirely possible theories, that could explain astrology naturally, inspired by new developments in physics, and even the old ones based on combined gravitational or electromagnetic field effects of celestial bodies can still be proven at some point. And to some extent, through their secondary observable effects like seasons and weather or Moon phases and tides, some basic effect of celestial bodies on living things and their psyche is evident. But there is also an entirely different class of physical explanations, based simply on the notion that celestial bodies only serve as a natural clock and that the whole of astrology is simply a function of time, which opens plenty of interesting testable possibilities, though no less complex. Astrology could be seen as an equivalent to a computer algorithm, some form of simultaneously entagled quantum resonance between living and/or non-living things, psycho-social instinctual response to perceived temporal cycles, etc. There is a number of valid recent scientific theories ranging from physics to sociology, allowing astrology and inviting testing. Only the outdated mechanistic theories of nature do not make astrology possible.
But ultimately, astrologers do not seek scientific proof of their method, and this is the part where astrology actually isn't science and parts its ways with conventional psychology. However, there are more similarities than you might think, and other reasonable (intelligent, logical, empirical) ways of looking at the world than just the scientificic method. You may like (and disbelieve) that in astrology, no faith is required. You can test whether any tenet of astrology works for yourself on yourself, on the people you know, comparing it by trying the same on the people you at the moment don't know and finding all about them after you make them a reading, and so on. That is why I keep repeating that astrology is empirical - based on repeated observation and experience. Whatever an actual astrologer claims about any aspect of anything, it is based on what they observed. It would be their interpretation of course, and they may have made a bad call, and you don't have to accept it, if you try it and it fails to apply. No dogma here. There really should be much less consensus among astrologers than there is, if it all is just random gibberish, precisely because there is this personal proto-form of peer review going on since the beginning of astrology, which has been thousands of years. The only thing that astrological evidence isn't which science requires is intersubjective - evidence can not be shared objectively and neutrally from person to person, if it is a personal observation. Sceptics may object on several grounds here, saying that people will selectively remember only successes and forget misses, or that personal experience is inevitably biased. The answer to that would be of course, one has to cleanse himself of bias as much as possible and train his intuition. That is why doing astrology is frankly way more difficult than doing impersonal science, because it requires not just intelligence, but also character traits like integrity or awareness, which are unfortunately not required from scientists at all.
The method itself however is largely objective and founded in well-rounded holistic synthetic logic. Science picks things apart and studies small shreds under a microscope. That is why its findings in psycho-social domain either lack context or depth, in both cases producing very little useful meaning. Astrology works on the basis of a logic which emphasizes role of each part of the whole in the context of the whole, looking at both human mind and society as organisms in their own right. Astrology also recognizes that you cannot make impersonal statements about people and expect them to have any significance. However, given the frame of the whole always applies, no particular opinion or position is isolated or arbitrary or relativistic, meaning that even personalized views are still universally valid and can be objectively analysed. For instance, where psychology considers occupation, race, gender, class and other impersonal characteristics to be important, for astrology they are irrelevant. Conversely, astrology cares about inner, essential characteristics and archetypical roles, understanding actions more in terms of a story unfolding - what play are you in, what is your part and how are you internally identifying with it. It may not be important that you are a black female soldier, but it matters that you are a determined and obedient person deciding about who lives and who dies. In astrology, you could be the same person if all listed impersonal characteristics were different, or an entirelly different person, if they remained the same. Science assumes that you cannot see into people, even though what's in there really matters, and you cannot. If you do not engage yourself at a personal level and use your intuition, ideally guided by archetypal heuristics like astrology. Or psychoanalysis, a shameless ripoff of astrology.
CONCLUSION: Astrology is very methodical and founded in sound logic, it differs with science only in the way of looking at things, and for good reasons too - what is a "black box" to science is the only part of people that really matters in astrology. Acclaimed methods like psychoanalysis which see it similarly are after all derived from classical astrology and other hermetical disciplines anyway.