For those that are sincerely interested in how astrology might be relevant to financial planning, I'll try to write this in non-astrologer terms.
Because my time is limited, I will not answer critics that astrology is "pseudoscientic nonsense." I've written in other places about why it is not, (my blog specifically) and have publicly argued with these critics in forums like Quora where instead of providing reasoned answers these critics resort to ad hominem attacks, and insults. This is their last resort because they have NO proof of their claims. (And please don't waste my time with Carlson, the supposed Time Twins study that has never been published, or the Star Baby incident. Asked and answered in other forums.)
1.) The planets move in cycles, as one person here noted. Certain financial astrologers have tracked the movements of the planet Jupiter (the planet of expansion) and Saturn (the planet of constriction) as indicative of stock market expansion and contraction. Astrologer Barbara Koval wrote about these extensively in her out-of-print book, Time and Money and how they relate to market cycles. Unfortunately, even for trained astrologers, the material can be dense and you need a thorough grounding in astrology before you attempt to read it.
2.) In my experience, because the planet Pluto is the planet of the rich, money in the markets, and the Plutocracy in the US (Pluto is prominent in the US natal chart in the second house of money,) and the planet of sudden charges, Uranus can shake things up, you need to toss those into the mix.
3.) Even with those four planets and the other transits at the time of the reading, you need something to read them against. These would be in my experience the Dow Downs "natal" chart (the planets as they sat on the inception of the market,) and the Sibley chart of the United States (if you are speculating in US markets.) Also, you need the "natal" chart of the individual company or fund you are interested in. Many astrologers (because many have not had that depth of training) have trouble reading three charts together, let alone four or five.
4.) The interpretation comes from a careful consideration of all the factors. It's not as simple as saying "Jupiter sits in the second house of money in the United States chart so the market will expand. You need to evaluate how the other planets both transiting and natal interact with each other. For instance, the planet of transformation Pluto has tenanted the zodiac sign of Capricorn since January 2008 in the US money sector, and most of us remember how tumultuous that year was. In addition, entrances and exits from one sign to another, or from one house to another in the chart you are studying signal seismic shifts. (I can hardly wait when Pluto moves into the sign of Aquarius in January 2024.[sarcasm])
For instance, when the planet of stability, Saturn, in the sign of constrictive Capricorn crossed the US first house cusp (the ascendant—outward appearances) on February 5, 2018, the US saw a precipitous drop in the stock mark—the lowest of the year. According to Business Insider 2018 had a -4.4% return on stock investment.
It's not enough to say that astrology works in cycles, even though it does to a great extent. You need to look for similar kinds of events within astrological symbolism to make your predictions. Each zodiac sign has a ruling planet, so you look at both the sign and then the planet that rules it to find their influences. And this takes a trained astrologer who has also studied financial markets, and these folks are rare birds in astrology. So it's a difficult study, but not an impossible one.
If you were to seek the advice of an astrologer for finances they would look at your entire chart but pay specific attention to the second (your money house,) the eighth (other people's resources), the planets in those houses, if any, the zodiac signs on the cusps of those houses, and the planets that rule those zodiac signs, and the planets transiting those house. I've been able to reliably tell disbelieving when they would get a raise, or when to start a business, what resources were available to them.
Don't ask me when you'll win the lottery. You'll be disappointed. From what I can figure out you need to be in the area the ruling planets of individual lotteries are passing overhead when the numbers are drawn to win. Even then there is no guarantee you'll be the person winning and not any of the other thousands in the area. If I could get the birthdate of lottery winners, I could make a hypothesis after studying their charts why they won, but that data is not available.
So there is a method in using the planets for financial planning, and it makes sense to astrologers, but I'm afraid it sounds like so much goobley gook to non-astrologers so it's not of use to most of you. Astrology, especially financial astrology is not DIY project, and it's not an easy study.
That's as good as I can explain it.
Credentials: Practicing astrologer since 1986, Astrology Explored blog from 2008 to present, and wrote the e-Financial Times yearly horoscope from 2011 to 2015 until a new editor decided it was too silly a subject to put in their publication.