What this product claims, and what it does not

What this computes · Swiss Ephemeris, ET for positions, UT for houses · 22 bodies · 6 house systems · 9 aspect types, adjustable orbs · what it does not claim: that astrology is true, or that it is false

01What is actually computed

Start with the arithmetic, because it is the only part of this page that is checkable rather than a matter of opinion. A Lizastro chart's planetary positions come from Swiss Ephemeris — the ephemeris Astrodienst has maintained since 1997 and the de facto standard the rest of the astrology-software industry builds on. Positions are computed in Ephemeris Time, the uniform timescale the underlying tables are built on; houses and the four chart angles are computed separately, in Universal Time, because a house wheel depends on the Earth's actual rotation in a way a planet's orbital position does not. Getting from a birth record to either timescale means resolving a local clock reading through the historical time zone that applied at that place on that date, daylight-saving transitions included — a real conversion, done in full, not skipped or approximated away.

Twenty-two bodies are available: the ten classical and modern planets every chart carries by default, plus both variants of Black Moon Lilith, both the mean and true lunar nodes, Chiron, and four of the larger asteroids — Pholus, Ceres, Pallas and Juno. All twenty-two cost the same single engine call to compute; none of them is held back for a later, paid step. Six house systems are available, Placidus by default, with whole sign, Koch, equal, Porphyry and Regiomontanus alongside it, and every chart states which one produced its house placements rather than leaving the choice implicit. Aspects are found across nine defined angles — conjunction, opposition, trine, square, sextile, quincunx, semisextile, semisquare and sesquiquadrate — each checked against a stated orb, widened by a fixed factor for the Sun and Moon, and narrowed automatically for a moving transit rather than a fixed natal contact. Every one of those settings is adjustable, and every chart is stamped with the exact settings used to produce it.

The default zodiac is tropical — 0° Aries is the vernal equinox. Sidereal (Lahiri IAE-1985) is a chart-settings option behind a feature flag; nakshatras, dashas and vargas are not computed.

That is the entire computational claim: a specific, named ephemeris, a specific and disclosed set of default settings, all of it changeable, and a record on every chart of which settings actually ran. Nothing about that claim depends on whether astrology, as a practice, describes anything real about a person. It is a claim about arithmetic, and it is either correct or it is not, independent of any belief about what a planet's position means.

02What reaches the interpretation, and what does not

The step between a computed chart and a written sentence about it is where most astrology products stop being checkable, and it is worth stating plainly what happens on this one. The interpretation layer never receives free text about a person — no name, no life story, no open-ended prompt asking a model to write something astrological. What it receives is structured data straight from the chart itself: which body, in which sign, at which exact degree, in which house, in what aspect to what else, at what orb. A sentence produced from that pipeline can be traced back to the specific placement that produced it, because nothing else was available to produce it from. Asking the same question about the same chart twice returns a reading tied to the same underlying data both times, because the data, not a fresh guess, is what the sentence is built from.

This is a constraint on the interpretation, not a claim about its wisdom. Restricting the input to structured chart data makes a sentence traceable; it does not make the sentence's underlying premise — that a planet's position at birth says something meaningful about a person — either more or less true. The constraint is the whole of what this page claims about the writing: it stays tied to the geometry, and the geometry is shown alongside it rather than hidden behind it.

It is also worth separating this claim from a claim about the model doing the writing. The interesting fact here is not that a language model is involved at all — a model is a tool for turning structured data into readable sentences, and naming it is not a selling point on its own. What is worth stating is the boundary placed on what the model is allowed to see: chart data and nothing else, no matter which model happens to be running the writing step on a given day. A model swapped for another one under the same constraint would produce different sentences and the same traceability, because the traceability comes from the constraint on the input, not from any particular model's judgment.

03Where the uncertainty actually is

Three specific places in the pipeline carry real, named uncertainty, and each one is handled by showing the uncertainty rather than picking a plausible-looking number and moving on. When a birth time is not known, the engine still computes the Sun, the Moon and every other body's sign using an assumed noon, which bounds the Moon's possible error to roughly six and a half degrees in theory — stated conservatively as up to about seven — while the Ascendant, the Midheaven and every house cusp are left out of the chart entirely rather than filled in with a noon-derived guess, because there is no bounded, honest version of an Ascendant computed without a real time.

When a birth is dated before 1970, the underlying time zone database that converts a local clock reading into a precise offset is not considered fully reliable outside of the specific city that defines a given zone, so that chart's confidence rating is downgraded and its Ascendant is flagged as able to drift by roughly a degree even when the clock time itself is known and trusted. And every displayed orb, house system and aspect angle carries the disclosure that it is a stated convention rather than a discovered constant — a widely used default in modern practice, adjustable by anyone who wants a stricter or looser reading, never presented as the one correct tolerance the sky itself enforces.

None of these three are edge cases carved out for completeness. They are the specific, nameable places where this product's own confidence is genuinely lower than usual, and the choice made in each one is the same: measure the uncertainty, carry it through the calculation, and show it on the result, rather than rounding it away in either direction.

04What this product does not claim

It does not claim that astrology is true, and it does not claim that it is false. Both are arguments this page deliberately declines to make, because the actual claim underneath the product is narrower than either one: that the calculation is correct and checkable, which is a question with a real answer, rather than that the practice built on top of the calculation describes something real about a person's life, which is a question this page is not equipped to settle and does not attempt to.

It does not claim to be more accurate than Swiss Ephemeris itself, or more accurate than any other tool built on the same ephemeris — the underlying planetary theory is the same one Astrodienst's own site runs, and a chart computed here for a given birth should agree with a chart computed there for the same birth, because both are reading the same tables. It does not claim to predict what will happen to anyone, on any day, under any transit — a transit's dates and the aspects it forms are computable in advance and stated as exactly that: dates and geometry, not forecasts of outcomes. And it does not claim to be "accurate astrology" as a single blanket phrase, because that phrasing quietly asserts the very thing this section has just said the product takes no position on. What is accurate, specifically and only, is the arithmetic — the position of a body at a given moment, the angle between two of them, the cusp of a house under a given system — and that word is used here for that, and nothing wider.

Money follows the same discipline the calculation does. Computing a chart, seeing its wheel, its planet list and its aspect table costs nothing and requires no account at all. An account is what a reader needs to keep a chart, to get a daily reading built from it, and to use Circle — not because those are hidden behind a price, but because they require somewhere to save to. A further, not-yet-open tier is planned to add longer-form reports and unlimited comparisons between charts later; nothing about that plan changes what the free calculation already shows in full today.

05Where you see all of this in your own chart

Every claim above is checkable against the same page a reader would use to compute their own chart. The engine version, the timescale split, the body count, the house-system default, the orb table and the birth-time confidence rating are not marketing copy sitting apart from the product — they are read from the same code that computes the chart, printed on the result, and open to being wrong in a way that would be visible rather than merely asserted. A reader who wants to check any single figure in this article against the calculation that produced it can do so on the same chart, with the same settings, stamped in the same place every time.

→ Compute your own chart · Read the full methodology

06Related reading

The unknown-birth-time article covers the noon assumption and the Ascendant's absence in full detail, for the specific case this page only summarises. House systems and the orb article both cover a stated-convention-not-a-law point from the other two directions this page draws on — six ways to divide a wheel, and a tolerance table borrowed from a school of practice rather than measured from the sky.

Updated 2026-06-10.