How MOON reads.
Most horoscope sites run on a sun-sign lookup table and a copywriter. This one runs on astronomy we run ourselves and two written traditions — and it will show you its work. If you're deciding whether to trust a fortune site you found through an ad, this page is for you.
1 · The astronomy is real
Your chart is worked out in your browser, on your device, by our own implementation of the algorithms in Jean Meeus' Astronomical Algorithms together with JPL's published approximate orbital elements. Geocentric positions for the Sun through Pluto, the Ascendant and Midheaven, houses, aspects, with nutation and ΔT handled properly.
Most astrology sites advertise a single accuracy number for the whole chart. That number cannot be honest, because the bodies are not all worked out the same way. So here is ours body by body, measured against NASA JPL's own ephemeris rather than assumed:
Sun and Moon — inside one arc-minute. Across 1900–2050, every sample stayed under it. These come from Meeus' own series, and they are the two bodies nearly every reading turns on.
Ascendant and Midheaven — geometry, not approximation. They fall out of sidereal time and your birthplace coordinates, so no ephemeris error reaches them at all. The only thing that moves your Rising sign is your birth time being wrong, which is why we keep asking for it.
Mercury, Venus, Mars — a few arc-minutes. Comfortably enough for a sign, a house and an aspect.
Jupiter through Pluto — up to about a quarter of a degree. These run on approximate elements with no aberration correction, and that is a real limit, not a rounding. In a large sample of charts it shifted a printed degree by one in roughly one chart in six, and put a planet in the neighbouring sign in about one in 226. Everything else in the chart was unaffected.
So: the Sun, the Moon and the Rising sign — the three placements a reading actually stands on — are tight to the arc-minute. The slow planets are approximate, and we would rather print that than average it away into a slogan.
The date-picking math is checked against reality, not against vibes. It works out its own eclipses from the lunation elements — nothing is read off a list — and we then diffed every one against the NASA Five Millennium eclipse catalogues (Espenak & Meeus) across 1901–2100: 909 catalogued eclipses, none missed, none invented. For 2001–2100 our solar total / annular / hybrid split matches NASA's own century count exactly — 68, 72 and 7. Where a classification falls inside our own error bar, we print "solar eclipse" and refuse to name the type. Retrograde stations are solved to the instant by bisection, not copied from a blog's list.
2 · The Western rules come from the tradition's books
For timing questions — wedding dates, launches, signings — we apply classical electional astrology: the branch of the tradition concerned not with what a day means but with which day to pick. The rules we check are the documented ones: Mercury retrograde periods, the void-of-course Moon (the span after the Moon's last Ptolemaic aspect before it changes sign), eclipse seasons to avoid, benefic and malefic aspects to the day's Moon. Every verdict carries its reasons — a degree, a time, a named aspect — so you can see what the call was made on instead of taking it on faith. The Moon drives most of that scoring, and the Moon is the part we hold to the arc-minute; where a reason rests on Jupiter or Saturn, the breakdown above is the tolerance to read it with.
3 · The Eastern rules come from the four-pillars method
The second opinion comes from the four-pillars method. It was codified in Song-dynasty China and has been read across East Asia ever since; it is not any one country's invention, and we won't sell it to you as one. MOON reads it in the Korean lineage of that method — the reading a Seoul fortune house would give you. Your birth moment becomes four pillars (year, month, day, hour), taken from the true solar terms — the Sun's actual longitude, not calendar months — which is where lazy implementations go wrong. From there: your Day Master and the element balance — and the ten-year luck cycles when you answer the gender question, which is the only thing that sets which direction they run.
4 · The rule that makes it honest
We tell you where it doesn't hold. A Western chart and an East Asian four-pillars chart are independent readings of the same birth moment. Where they point the same way, MOON says so — as something worth noticing, not as proof. We checked whether that agreement means anything: across 22,280 birth dates the two systems landed on the same word 54.9% of the time, and on deliberately mismatched dates they landed together 53.2% of the time. Your own two counts do beat a stranger's, by about 1.7 points — but not because the traditions confirm each other. The entire margin sits in the Eastern year pillar, which changes its element every 2 years while Saturn changes sign every 2.46, so where the two agree above chance they are reading the same slow clock twice. We publish that instead of selling it. Where only one system flags something, the reading tells you which one. Where the data is missing — no birth time means no rising sign — MOON tells you what can't be known instead of guessing.
How a paid reading actually gets written
The chart math and the rules above are the skeleton, and the reading is written on top of that skeleton — which is why every claim in a reading carries its chart anchor (the placement, the degree, the month). Readings that come back without their anchors, or padded, or off-voice, are rejected by our quality checks and rewritten before you ever see them. What you read was written for your exact chart, once, and never recycled for the next customer.
What we won't do
- Flatter you. We run a banned-phrase list — "the universe wants", "manifest", "trust the process" and their cousins don't survive our checks. If your chart has a hard angle, you'll read about the hard angle.
- Scare you. The opposite trick is worse. A bad day in a reading is a caution — "sign nothing that Tuesday" — never doom. Fear is how scam fortune sites upsell curse removal. We don't sell curses, so we don't need you afraid.
- Trap you in a subscription. Every product is a one-time purchase. There is nothing to cancel, because nothing renews.
- Wall the free reading behind your email. The free chart takes a birthday and three seconds. No signup, no email gate.
- Invent trust. No fake astrologers with fake diplomas, no purchased five-star reviews, no invented user counters. What you see cited on this site is real: Meeus, JPL's published elements, the classical electional literature, the four-pillars canon, NASA's eclipse records.
- Round our own error off. This site used to advertise "arc-minute accuracy" for the whole chart. We checked it against NASA JPL, found that Jupiter and Saturn do not hold that line, and rewrote the claim rather than the measurement. The breakdown is in section 1, and it is the reason to believe the rest of this page.
- Pick dates where the stakes are a body or a grief. We refuse to pick "auspicious" dates for surgery or for funerals, even though people search for both. A party can move a week; those can't. That boundary is written into the site's code.
Talk to us
A question, a wrong-feeling reading, a delivery problem, a deletion request — one address, read by a person: moondontlie@gmail.com.
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