tl;dr: You can make money using financial astrology. You might even beat the market with it.
My father is a physicist. He spent much of his career analyzing data, and when I was a kid he showed me how he could take pretty much any set of linear (non-random) data points, and he could find an equation that would yield those points. I once asked, "But is that really useful? Was matching to existing data predictive of new data points?" He told me, "Sometimes it ends up being predictive, and when it is it's a lot more fun! And then I might get another patent..." (He has over 100 patents.)
Humans are wired to notice patterns and predict future events based on them; it's one of our survival mechanisms. Some people are much better at it than others, and this is true in pretty much all aspects of life. The thing that makes astrology in particular so compelling is the fact that it's cyclical, and there are so many objects with various cycles that you can pretty much match any set of historical data points to something celestial if you try hard enough. But obviously the interesting question is whether or not it's predictive of future data points. Well, on average, in relation to stock markets, the markets are generally increasing, so it doesn't matter that much as long as the decisions it guides you to make do not deviate too far from the norm. You'll make money at approximately the same rate, but it just might be a heck of a lot more fun, especially if you believe in it. And if you do end up beating the market (which you might just have a 50% chance of doing any particular year), who's to say you can't go on to write some books and start teaching it to other people?
If you aren't satisfied by this answer yet, then consider this: celestial objects were set into motion nearly 14 billion years ago. The observable patterns of bodies are well known, and can be predicted from long ago to far into the future. Stock market fluctuations are a direct result of human reactions to corporate decisions, national and world events, and the way the news media reports on those events. If you believe celestial bodies are causing pandemics, technological breakthroughs, acts of war and terrorism, political maneuvers, corporate decisions, and the way the media reports on them, well, then, I promise you, we probably could have known a billion years ago (but definitely 100 years ago), that Jupiter was going to do that interesting thing tomorrow. It doesn't mean it's time to buy more gold.
Further reading in this answer.