How Luune calculates your chart
Astrology apps have a trust problem: too many feel like random text generators. Luune isn't one. The positions under every chart we draw are derived from NASA JPL's DE431 ephemeris — the same family of data used to fly spacecraft — and placed to within an arcsecond. Here's exactly how it works.
Where our data comes from
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An ephemeris: a precise map of the sky
Every astrology calculation starts from one question — where was each planet at a given moment? The answer comes from an ephemeris: a high-precision table of planetary positions across time.
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NASA JPL's DE431
Our positions trace back to DE431, an ephemeris computed by NASA's Jet Propulsion Laboratory — the same family of data used to plan spacecraft trajectories. If the map were off, the spacecraft would miss.
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The Swiss Ephemeris
We read that data through the Swiss Ephemeris, the same engine professional astrology software relies on. It places every planet to within roughly one arcsecond — 1/3600th of a degree.
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Your exact birth moment
We combine that sky with your birth date, time and place — converted to precise universal time using your birth city's historical timezone rules — to build your chart for the moment you arrived, not a sun-sign shortcut.
The one-line version: planetary positions trace back to NASA JPL's DE431 ephemeris, via the Swiss Ephemeris.
How accurate is it?
A single degree of sky is about the width of two full moons side by side. We place each planet to within one arcsecond — 1/3600th of that degree. It's the same standard professional astrologers use in desktop software like Solar Fire, and far finer than any reading needs.
That precision carries through to the moving parts most apps get wrong: retrograde motion is detected from each planet's real measured speed rather than a lookup table, new and full moons are refined to the hour, and we compute the True Lunar Node — the Moon's actual orbital wobble — not the simplified Mean Node. Chiron and Black Moon Lilith are computed too, not faked.
Why your exact birth time & place matter
Most apps just guess your timezone. We look up the exact rules your birth city followed that year — including whether daylight saving was in effect — and convert your birth moment to precise universal time from there. Then your real Ascendant and house cusps are calculated from your exact latitude and longitude.
This is the single biggest difference between a chart that's actually right and one that's a few degrees off. The Moon and rising sign move fast — a wrong timezone can hand you the wrong rising sign entirely.
What we calculate
Every one of these runs on the same engine — real astronomy, computed for your exact moment or for today's live sky.
Where astronomy ends and astrology begins
We're careful about one line. The astronomy is exact — we can tell you to the arcsecond where every planet sits. What those positions mean for you is the centuries-old language of astrology: interpretation, not physics. Our daily horoscopes are written by an AI guide, Mira, but always grounded in the real sky for that day — never invented positions, never a human expert passed off where there isn't one. We'd rather show our math than dress interpretation up as science.
Your birth data stays yours
Your birth date, time and place are the most personal things an astrology app can hold. We never sell, rent or share them. You can export everything or permanently delete your account at any time. The methodology on this page is the rest of the promise: we show you exactly what's under the hood.
Read the full privacy policy.
Frequently asked questions
Does Luune use NASA data?
Indirectly, yes. The planetary positions we calculate are derived from DE431, an ephemeris produced by NASA's Jet Propulsion Laboratory, read through the Swiss Ephemeris library. It is public astronomical data — we're not affiliated with or endorsed by NASA, but the math under your chart traces back to the same source NASA uses for mission planning.
How accurate is the astronomy?
Planetary positions are accurate to within roughly one arcsecond — 1/3600th of a degree. For scale, a single degree is about the width of two full moons side by side, so an arcsecond is far finer than any astrological reading requires. The accuracy is in the astronomy; the meaning of those positions is the interpretive tradition of astrology.
Why do you need my exact birth time and place?
The fast-moving points — your Ascendant, house cusps and Moon — change quickly, so even a few minutes matters. We convert your birth time to universal time using the historical timezone and daylight-saving rules your birth city actually followed that year. Getting that conversion wrong is the single most common reason cheap apps show the wrong rising sign.
Can you calculate charts before 1800?
Not yet. The bundled ephemeris covers roughly 1800 to 2399 CE, which includes every modern birth date. Charts for dates before 1800 currently fall outside that range.
Are the horoscopes pre-written?
No. Each daily and weekly horoscope is built from the real sky for that day — the actual transits, ingresses, retrograde stations and moon phases — and only then written up in plain language. The astronomy is computed fresh; the wording is an interpretation anchored to those real events, never invented positions.
Where does astronomy end and astrology begin?
The astronomy is exact: we can tell you to the arcsecond where every planet sits. What those positions mean for your life is the centuries-old language of astrology — interpretation, not physics. We keep the two clearly separate, and we never put a precision number on a life prediction.
Ready to see your own chart? Run the free birth chart calculator.