For developers · REST API
Precision, served — one sub-arcsecond call away.
118 REST endpoints computed against NASA JPL DE440 — natal charts, transits, synastry, astrocartography, Human Design, BaZi. Clean JSON in, exact positions out. No approximations, no license traps.
Powers ELA Map — a full locational-astrology and Human Design platform — in production.
- REST endpoints
- 118
- REST endpoints
- position error
- < 0.01″
- position error
- median latency
- ~85ms
- median latency
Capability grid
118 endpoints across 8 domains
Western, Vedic, Chinese, and astronomical traditions — all in one authenticated API. No license traps.
Natal & Chart
- Full natal chart with aspects, dignities, and lots
- 12 house systems (Placidus, Whole Sign, Koch, Equal…)
- Vedic / sidereal charts with nakshatra placements
- Chart rendering (SVG / PNG wheel output)
Predictive & Timing
- Transit forecasts with exact aspect windows
- Secondary progressions & solar arc directions
- Solar and lunar returns
- Electional window search
Relationship
- Synastry overlay (two-chart comparison)
- Composite (midpoint) charts
- Davison relationship chart
Astrocartography
- Planetary power lines (ASC/DSC/MC/IC)
- Crossing and paran analysis
- Location scoring and heatmaps
Human Design
- Full bodygraph computation
- Type, strategy, authority, definition
- Gates, channels, and incarnation cross
Chinese Astrology (BaZi)
- Four Pillars natal chart
- Ten Gods, luck pillars, annual pillar
- Element balance & compatibility analysis
- 24 Solar Terms
Calendar & Astronomical
- Lunar phases, void-of-course, eclipses
- Planetary hours & planetary days
- Ingresses, stations, retrograde windows
- Fixed star positions (110+ stars)
AI & Developer Tools
- LLM-optimised response format (50% fewer tokens)
- MCP server for Claude, Cursor, Gemini & more
- Timezone resolution from coordinates
- OpenAPI spec for Postman/Insomnia import
Technical specs
NASA-grade precision, developer-grade DX
Every position is computed from JPL DE440 — the same ephemeris NASA uses for deep-space mission planning. No approximations, no lookup tables.
Read the full developer guide →Pricing
Start free. Scale when ready.
150 free credits to start — no credit card. Wallet top-ups from $5, subscriptions from $29/mo ($22/mo billed annually).
Frequently Asked Questions
How many endpoints does this astrology API have?+
118 production REST endpoints covering Western natal, predictive (transits, progressions, returns), synastry, astrocartography, Human Design, Chinese BaZi, Vedic/sidereal, and astronomical calendar systems.
What house systems are supported?+
Twelve house systems: Placidus, Whole Sign, Koch, Equal, Regiomontanus, Campanus, Porphyry, Morinus, Alcabitius, Meridian, Vehlow, and Topocentric. Specify the house_system parameter on any natal chart endpoint.
Can I use this for Vedic (sidereal) astrology?+
Yes. All natal chart endpoints support sidereal positions via the ayanamsa parameter. Lahiri (Chitrapaksha), Raman, and Krishnamurti (KP) ayanamsas are supported. Vedic-specific endpoints include nakshatra placements.
Does this API support astrocartography?+
Yes. The astrocartography endpoints compute planetary power lines (ASC, DSC, MC, IC) for any natal chart, crossing analysis, paran lines, and location scoring with heatmap output. Available on the Pro plan and above.
Is there an LLM-optimised response format?+
Yes. Pass format=llm to any natal chart endpoint and the response is compressed to roughly half the tokens of the standard JSON format. A full natal chart fits in approximately 600 tokens instead of 4,000–8,000, which means faster and cheaper LLM inference.
Can I connect this to Claude or other AI assistants?+
Yes. The OpenEphemeris MCP server gives Claude, Cursor, Windsurf, Gemini CLI, and any MCP-compatible client access to 84 astrological tools. Install via npx @openephemeris/mcp-server or connect directly to the Streamable HTTP endpoint at mcp.openephemeris.com/mcp. Full setup guide at openephemeris.com/astrology-mcp.
What is the free tier?+
The Explorer tier is free — a one-time grant of 150 computation credits, no daily cap. A natal chart costs 1 credit. No credit card required to start. Sign up and get your API key immediately. Top up anytime from $5 — credits never expire.
How accurate is the planetary data?+
All positions are computed from NASA JPL Development Ephemeris DE440 — the same data source used for deep-space mission planning. Precision is sub-arcsecond across the full date range of 1550 to 2650 CE.
One API key. Every calculation.
Free tier. No credit card. 150 credits to start, top up from $5.
New to astrology APIs? Read our developer guide