The calculations are deterministic. I happen to know how astrologers work, and why people still believe them.

You run the algorithm using the exact time and place of client's birth. This is, of course, bullshit — some random predictions, which are deliberately written in quite ambiguous, but somewhat flattering style (the genre was perfected in hundreds of years). But now, the most interesting part comes to play.

You tell the client one or two predictions from the list, starting from the most vague and/or flattering (like "you are probably going through worse times than you deserve"), and observe the reaction. If it is positive, you probe the next close thing from the generated set, and so on. If you are good in reading people and adjusting your response according to body language feedback, you can generate the set of predictions or advices so accurate you will impress even yourself, even if you don't believe any of the astrological bullshit. Most astrologers don't.

Since Astrology is bunk, it might be interesting just to see what they're doing/claiming with this.

It's very unlikely astrologers have created or added anything that's useful or applicable to astronomy. It's more likely that they've taking things astronomers have discovered and used and worked that into their quackery to make slicker quackery.

Astronomy now is a science, but historically there wasn't any distinction and much astronometry (measurements of the sky) was done to increase the accuracy of the predictions.

It could well be they are doing epicycles caculations to determine stellar positions etc

Right: Astronomy is astrology which advanced beyond the pre-scientific mindset, and made progress, as opposed to stagnating. We can see similar progressions in the medical world, and we can see that one thing holds true: The scientific version of the field became useful to society as a whole, whereas the non-scientific one remains only useful to the practitioners, and then only to the extent they charge for their services.

I think it would be interesting if it was like a special-purpose calculator for astronomy, that happened to have pointless astrology window dressing.

I also think it would be interesting, albeit in a totally different way, to know what "algorithms" they're up to in there, even though it's bullshit.

Definitely agree about their quackery.

Interestingly, astrologers have made significant contributions to the history of timekeeping. Since they really care about clock changes, time zones, mean solar time, and exactly when these things took effect, they've done a lot of good helping us better document that history. (It shows up in the Unix TZ project)

Greater minds than yours esteemed astrology as the "noble art" - Claudius Ptolemy, Tycho Brahe, John Dee and Carl Jung to name a few. Have you actually studied astrology beyond newspaper sun signs? If not, you're not in a position to dismiss it.