01Ephemeris and time
Positions come from Swiss Ephemeris — the ephemeris Astrodienst has maintained since 1997 and the de facto standard in astrology software. You can change the house system, tighten the orbs, and choose which bodies appear, and every chart is stamped with the settings it was computed under. Watching a setting change the answer is the fastest way to learn how any of this works.
- Zodiac
- Tropical is the default — 0° Aries is the vernal equinox point. Sidereal (Lahiri IAE-1985) is available in chart settings. Nakshatras, dashas and vargas are not computed.
- Viewpoint
- Geocentric, apparent positions (light-time and aberration included).
- Timebase
- Planetary positions are computed in Ephemeris Time (ET); houses and the Ascendant in Universal Time (UT). ΔT comes from the ephemeris’s own table.
- Time zone
- Resolved from the historical zone table for the birth place and date, including known daylight-saving transitions — Turkey’s permanent UTC+3 since 2016 is in that table too.
- Precision
- Degree and arcminute are shown; seconds are computed internally but not displayed. A one-minute error in birth time moves the Ascendant by roughly a quarter of a degree — a standard astronomical approximation, not one of the engine’s own constants.
02Bodies
The engine defines twenty-two bodies and points; all of them are free on the natal chart — the extended layer is not behind a paywall (see pricing). Fourteen of them currently carry written interpretation; the rest still appear on the wheel and in the list with their degree — never hidden, never given an invented sentence.
The Ascendant and the midheaven are computed as chart angles rather than bodies, and only when the birth time is known. This engine does not compute a Vertex.
03House systems
Six house systems are available, and the choice is stamped under every chart. Systems divide the same sky differently — planets do not move, boundaries do.
Near the polar circle (roughly 66° latitude) a time-based system like Placidus can go undefined for part of the year. Swiss Ephemeris itself handles that case and falls back to Porphyry — Lizastro adds no special-case logic of its own here; the request goes straight to the ephemeris.
04Aspects and orb
An aspect counts when the gap between two bodies sits within its orb of the exact angle. Orbs can be tightened; narrowing one removes aspects rather than adding them. They are never widened — a wider orb would manufacture an aspect that is not there.
An aspect involving the Sun or the Moon gets a 25% wider orb than the table below — the traditional rule that luminaries carry more weight. (×1.25)
Each aspect is marked applying or separating — a fast body moving toward or away from the exact angle. Strength is a 0–1 scale: it rises as the orb tightens and as the average importance of the two bodies involved goes up. The reading engine writes about the strongest aspects first.
05Birth-time policy
When the time is unknown, the Sun and the slower-moving planets are computed assuming noon (local) at the birth place, and the chart says so. The Ascendant, midheaven, houses and house-based readings are not shown — an Ascendant produced from a noon guess is usually wrong, and this product does not present a wrong thing as certain.
The Moon moves roughly 13° a day, so the noon assumption is off from the real position by at most about 6.5° in the worst case — a birth at midnight. Where that puts the Moon close to a sign boundary, both possible signs are shown together.
Timezone records for your birthplace before 1970 are uncertain. Your rising sign may be off by a degree.
06The reading engine
The model never receives free text about you — no name, no message history, no notes. What it receives is the structured output of your chart: body, degree, sign, house, aspect type, orb. The system prompt requires it to stay with that data, and lets it cite a degree or house number directly in the text; nothing outside the data is invented. Which contacts a reading rests on is not marked sentence by sentence — it is the list underneath the reading.
07Birth data and Circle
Your birth date, time and place are visible only to you. What a Circle room sees is only as much of the computed output as you allow — never the raw data — and each member sets their own level, defaulting to the most private.
Your raw birth data (date, time, place) is never shared at any level.
08Verification
The compatibility example on the landing page is a real computation, and its birth data is public — check it against another ephemeris if you like. Expect zero difference against other Swiss-Ephemeris-based software, and at most a few arcseconds against a genuinely different ephemeris. Every number on this site — including the live sky line in the header — comes from the same Swiss Ephemeris call; there is no separate, lighter preview calculation anywhere on the site.
If you find a discrepancy, tell us — a change to how something is computed would move this page’s version number and the footer of every chart at once.