The chart comes first. The language comes second.
PathFinder separates deterministic calculation from interpretation. Here is what the software computes, which conventions it chooses, what changes without a birth time, and where AI enters.
Software calculates. Humans interpret.
PathFinder produces the chart data before any language model is involved. The model does not decide where a planet, house cusp, angle, or aspect belongs. It receives calculated facts and selected reference material, then writes an interpretation. Astrology remains an interpretive practice, and model-written prose can still be wrong.
From birth data to reading
The boundary between calculation and interpretation is deliberate. A reading follows this chain:
Resolve the moment
A local date and time, named IANA time zone, latitude, and longitude are resolved to a UTC instant. Daylight-saving gaps are shifted forward; when a clock time occurs twice, the earlier occurrence is used and the resolution is recorded.
Calculate the chart
The calculation engine derives ecliptic positions, houses, angles, aspects, and their applying or separating state. The same inputs, settings, time-zone data, and calculation version produce the same numerical chart.
Retrieve relevant references
For each reading section, PathFinder searches a curated astrological library by semantic similarity and full-text relevance, with category and placement filters where applicable.
Write the interpretation
A language model receives the calculated chart facts and retrieved reference text, then writes the prose. Numbers, dates, positions, and orbs come from the calculation layer—not from the model.
Calculation engine
PathFinder calculates fourteen bodies: the Sun, Moon, Mercury through Pluto, Chiron, the North and South Nodes, and Black Moon Lilith. The Sun through Pluto and the Moon are calculated with the open-source Astronomy Engine ephemeris. Chiron is integrated from a J2000 state vector. The nodes and Lilith use the explicit conventions below.
Chart outputs carry a calculation version that includes the engine revision, time-zone database version, and aspect-orb settings. This makes the assumptions behind a result identifiable when calculation rules evolve.
Astrological conventions
Different astrology programs can disagree while each is following its own settings. These are PathFinder's defaults and alternatives.
| Choice | PathFinder default | Details |
|---|---|---|
| Zodiac | Tropical | Sidereal is optional with Lahiri, Fagan–Bradley, Raman, or Krishnamurti ayanamsa. |
| Lunar node | Mean node | The South Node is placed exactly 180° opposite the mean North Node. |
| Black Moon Lilith | Mean apogee | The mean lunar perigee plus 180°. This is not osculating or true Lilith. |
| Houses | Placidus | Whole Sign, Equal, Porphyry, Koch, Regiomontanus, and Campanus are also available. |
| Polar houses | Porphyry fallback | Placidus and Koch fall back above 60° latitude; Regiomontanus and Campanus above 66°. |
| Aspect selection | Tightest match | When more than one aspect window could match a pair, PathFinder keeps the aspect with the smallest actual orb. |
Default aspect orbs
An orb is the allowed distance from an exact aspect. If either body is the Sun or Moon, PathFinder adds 2° to the configured orb. Members can customize these values; zero disables that aspect.
| Aspect | Exact angle | Default orb |
|---|---|---|
| Conjunction | 0° | 8° |
| Opposition | 180° | 8° |
| Trine | 120° | 8° |
| Square | 90° | 7° |
| Sextile | 60° | 6° |
| Quincunx | 150° | 3° |
| Semi-sextile | 30° | 2° |
| Semi-square | 45° | 2° |
| Sesquiquadrate | 135° | 2° |
| Quintile | 72° | 2° |
| Bi-quintile | 144° | 2° |
When the birth time is unknown
PathFinder stores “time unknown” as an explicit fact. It uses 12:00 local time as a neutral internal anchor so date-based planetary positions can still be calculated, but it does not pretend noon was the birth time.
The interface and interpretation layer omit the Ascendant, Midheaven, house placements, angle aspects, sect, and other time-dependent facts. Planetary degrees—especially the Moon—remain approximate because bodies move during the day. A noon chart is not a rectified chart.
What AI does—and does not do
PathFinder readings are model-written. The model synthesizes calculated chart facts with retrieved passages from a curated astrological library. Retrieval narrows the material to the section being interpreted; it does not turn astrological interpretation into an objective measurement.
The model does not calculate the chart. It can still overstate, omit context, or phrase an interpretation poorly. Treat its output as a structured first pass for reflection or practitioner review, not as certainty, diagnosis, or a prediction of events.
Public calculation benchmark
The calculation accuracy benchmark publishes 44 JPL longitude checks, 48 Swiss Ephemeris house-cusp checks, six transit and station timing checks, and three historical IANA time-zone cases. Every raw row, frozen tolerance, source, and limitation is available as downloadable data. It measures deterministic calculation only—not interpretation or event prediction.
In one sentence
PathFinder calculates the astronomical and astrological structure in software, retrieves relevant reference material, and clearly labels the prose that a language model writes from it.
Inspect your own chart
Create a free chart and see the placements, houses, aspects, and interpretation together.