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Western Astrology API — Charts, readings and relationship work.

Natal, synastry, composite, Davison, returns and progressions — each one returning the calculation and an astrologer-written reading in the same response. Twenty-three house systems, tropical zodiac, one JSON contract.

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70+
Endpoints
23 house systems
Houses
<50ms
Median latency
JSON
Documented fields
  • 23 house systems Placidus, Koch, Campanus, Regiomontanus, Whole Sign and more.
  • True or mean nodes Switch node type with one parameter, Western or Vedic.
  • Location search included City lookup with coordinates and IANA timezone. No Google Maps bill.
  • DST handled Applied automatically from the date and place.
  • Authored predictions Written by an astrologer, not a model.
  • One JSON contract Same envelope and error semantics across every endpoint.
03 / What you can build

Everything a Western astrology app needs. Already built.

All of it running on calls you can make this afternoon.

Natal chart

  • Planets with sign, house and speed
  • Houses in 23 systems
  • Aspects with orbs and applying flags
  • Ascendant and Midheaven for each

Synastry

  • Every inter-aspect between two charts
  • Sixty readings from one call
  • Tense and harmonious flagged
  • House overlays both ways

Composite & Davison

  • Midpoint composite chart
  • Davison time-space chart
  • Own ascendant and Midheaven
  • Chart image for both

Transits

  • Live positions over the natal chart
  • Aspects to natal planets, with readings
  • Which house each transit falls in
  • Transit cusps and charts

Sky events

  • Sign ingress dates, planet by planet
  • Retrograde and direct stations
  • Eclipses and moon phases
  • Upcoming feed — build the notifications

Solar returns

  • Return moment to five decimals
  • Full chart for the year ahead
  • Return period start and end
  • Sell it as a yearly product

Progressions

  • Secondary progressions
  • Solar arc directions
  • Progressed against natal
  • Chart image included

Chart patterns

  • Shape — Locomotive, Bowl, Bundle and more
  • Occupied and empty arc in degrees
  • Leading planet identified
  • Stelliums by sign and by house

Balances

  • Elemental, weighted and unweighted
  • Modality distribution
  • Hemisphere emphasis
  • Which planets sit in each

Traditional dignities

  • Domicile, exaltation, detriment, fall
  • Triplicity, term and face
  • Peregrine flagged, scored
  • Chart sect, diurnal or nocturnal

Arabic parts

  • Fortune, Spirit and the rest
  • The formula that produced each
  • Sign, degree and house
  • Day and night variants

Fixed stars

  • Conjunctions with orb
  • Star magnitude
  • Planetary nature of each star
  • Keywords for interpretation

Deeper technique

  • Midpoints and midpoint trees
  • Declinations and parallels
  • Antiscia and contra-antiscia
  • Dispositor chains, void of course

All of it live today. Nothing on a roadmap.

04 / Predictions

Birth chart readings, written by an astrologer

Nineteen prediction endpoints. Versioned text you can put straight on screen — no model in the request path.

One call · ascendant-report · Aries rising

You meet the world head-first. Aries rising gives you an unmistakable directness — a quality of presence that walks into a room and immediately changes its energy. People notice you before you speak because your body language broadcasts confidence, urgency, and a readiness for action that most people only achieve after three coffees.

Cardinal fire Mars-ruled Verbatim from the API
Nineteen readings, ready to ship
AscendantSun sign Moon phasePlanet in sign Planet in houseHouse rulers AspectsAspect patterns Chart patternStellium RetrogradeElemental balance Modal balanceHemisphere Solar returnSynastry aspects Synastry housesTransit aspects
Token bills

No model sits in the request path, so a million readings cost the same as one.

Hallucinations

One synastry call returns sixty aspect readings, each written once and reviewed.

An astrologer on payroll

Same chart, same words, every time.

Readings, not just numbers

Nineteen prediction endpoints. Ascendant, sun sign, moon phase, stelliums, retrogrades, chart patterns and synastry aspects all return written text alongside the calculation.

23 house systems

Placidus, Koch, Porphyry, Campanus, Regiomontanus, Morinus, Alcabitius, Topocentric, Whole Sign and more — switch with a request parameter.

Relationship astrology

Synastry inter-aspects with per-pair readings, midpoint composite, and Davison time-space charts. Sixty aspect readings from a single synastry call.

Traditional and modern

Essential dignities with sect, Arabic parts with their formulas, fixed-star conjunctions with orbs — alongside midpoints, declinations and antiscia.

02 / Tropical Zodiac · Modern Western

All Western Astrology endpoints

Every endpoint returns structured JSON with documented fields, validated coordinates, and IANA timezone IDs.

70+
Endpoints

Natal Chart

21 EP

Planets, houses in four systems, aspects, dignities, midpoints, declinations, antiscia, Arabic parts, fixed stars, chart shape and balances.

  • POST /api/v3/western/natal/planets
  • POST /api/v3/western/natal/houses
  • POST /api/v3/western/natal/dignities-table
+18 more in the docs →

Predictions

19 EP

Written readings — ascendant, sun sign, moon phase, stelliums, retrogrades, house rulers, chart patterns, plus synastry and transit interpretation.

  • POST /api/v3/western/predictions/ascendant-report
  • POST /api/v3/western/predictions/synastry-aspects
  • POST /api/v3/western/predictions/moon-phase
+16 more in the docs →

Compatibility

10 EP

Synastry, midpoint composite and Davison time-space charts, each with its own chart image endpoint.

  • POST /api/v3/western/compatibility/synastry
  • POST /api/v3/western/compatibility/composite
  • POST /api/v3/western/compatibility/davison
+7 more in the docs →

Transits & Sky Events

14 EP

Live transit positions and aspects to natal, plus sign ingress, retrograde stations, eclipses, moon phases, combustion and a raw ephemeris.

  • POST /api/v3/transit/western/ingress
  • POST /api/v3/transit/western/retrograde
  • POST /api/v3/transit/western/eclipses
+11 more in the docs →

Forecasting

7 EP

Transits over the natal chart, secondary progressions, solar arc directions and solar returns.

  • POST /api/v3/western/forecasting/transits
  • POST /api/v3/western/forecasting/progressions
  • POST /api/v3/western/forecasting/solar-return
+4 more in the docs →
Frequently asked

Natal chart and Western astrology API — questions before you build.

Is there a free natal chart API I can test without a card?
Yes. StarsAPI's free tier lets you evaluate any endpoint without entering a credit card, so you can calculate a real birth chart and see the response before committing to anything. Paid plans start at $29 a month and carry every endpoint on the platform, with no per-product locks.
How do I add birth chart calculations to my app?
Send the birth date, time and place, and the chart comes back as JSON — planets, houses, aspects, angles and dignities. Place lookup and timezone resolution come with the same plan, so a city name is all you need from the user rather than coordinates. A working natal chart screen is usually a day's work.
Is there a synastry API for relationship compatibility?
Yes. Synastry compares two natal charts across every planetary pair, returning inter-aspects with exact orb deviation and whether each is tense or harmonious. One call comes back with around sixty aspects, each carrying its own written reading, plus house overlays in both directions — enough to build a compatibility product on, not just a percentage.
Which house systems are supported — Placidus, Koch, Whole Sign?
All three and twenty more, chosen with a single request parameter: Placidus as the default, Koch, Porphyry, Regiomontanus, Campanus, Equal, Whole Sign, Morinus, Alcabitius, Topocentric, Meridian, Vehlow, Krusinski, Sripati, Gauquelin and others. Ascendant and Midheaven come back for every one, so you can let a user pick the system their astrologer uses.
Can I generate composite and Davison charts?
Yes. Composite charts use midpoints between two natal charts; Davison charts use the time-space midpoint, which is a real astronomical chart calculated for the average moment rather than an average of positions. Each has its own chart-image endpoint.
Does the API calculate solar returns and progressions?
Yes — secondary progressions, solar arc directions and solar return charts, with the return moment resolved to a fraction of a degree of solar longitude. Solar return season is a reliable revenue event for anyone selling readings.
Does the API return interpretations, or only calculations?
Both. Nineteen prediction endpoints return text written by an astrologer and versioned — ascendant, sun sign, moon phase, planet in sign and house, house rulers, chart patterns, stelliums, retrogrades and elemental balance, plus synastry and transit interpretation. A chart of numbers is a developer's output; a reading is a product.
Does it support traditional and Hellenistic technique?
Yes, properly. Essential dignities with domicile, exaltation, triplicity, term and face, scored and with chart sect. Arabic parts with the formula that produced each one. Fixed-star conjunctions with orb, magnitude, planetary nature and keywords. Antiscia, declinations, midpoints, dispositor chains and void of course. This is the layer that traditional astrologers check for first and rarely find.
Can I track transits, retrogrades and eclipses?
Yes — live transit positions and aspects to a natal chart, plus sign ingress dates, retrograde and direct stations, combustion, moon phases, eclipses, a raw ephemeris, and a merged feed of what is coming up. Enough to run a daily notification product from.
Can I set my own aspect orbs?
Yes. Sensible astrological defaults are applied, and both major and minor orbs are customisable per request. Every aspect returned carries applying and separating flags and its exact orb deviation, so nothing is hidden behind a threshold you cannot see.
Can I get natal chart wheel images?
Yes — wheel charts in your choice of house system, rendered on our side and returned as an image you can drop straight into your app. There is no charting library to add to your codebase and nothing to maintain when your framework changes.
Can I put my own brand on it?
Yes. Nothing in a response identifies us, and the written reports carry your name, tagline, website and logo on every page. What your users see is your product.
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