Swiss Ephemeris · Open Source · AGPL v3 Licensed · Free to Use

Precise astronomical
calculations for
every application

A production-grade ephemeris API powered by the Swiss Ephemeris. Free for development and low-volume use. Open source — run your own instance.

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⊕
Geocentric & Heliocentric

Full dual-frame position data for all major bodies, asteroids, and special points.

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15 House Systems

Placidus, Koch, Whole Sign, Regiomontanus, Equal, and ten more — switchable per request.

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Predictive Techniques

Secondary progressions, solar arc directions, solar and lunar returns all in one API.

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Ephemeris & Events

Monthly ephemeris, lunations, apsides, and next-event finders for any date range.

Simple by Design

One request.
Complete data.

A single POST to /calculate returns geocentric and heliocentric positions, house cusps, angles, and all configured celestial bodies. Every field is configurable per-request or set once in your key's output configuration.

POST /calculate 
// Request
{
  "chart_name": "Albert Einstein",
  "datetime": "1879-03-14 11:30:00",
  "location": "Ulm, Germany",
  "house_system": "placidus"
}

// Response (excerpt)
{
  "chart_id": "a3f2c1d4-...",
  "planetary_positions": {
    "sun": {
      "longitude": 354.098,
      "retrograde": false
    }
  }
}
POST /calculate Calculate natal or event chart
POST /chart/{id}/solar-return Solar return for a given year
POST /chart/{id}/lunar-return Lunar return for a given month
POST /chart/{id}/progressions Secondary progressions
POST /chart/{id}/solar-arc Solar arc directions
POST /ephemeris Full month ephemeris at noon UT
POST /apsides Lunar and planetary apside positions
POST /apsides/next Next apside events over any window
POST /lunations New/Full Moon and quarter events
GET /chart/{id}/derived List derived charts for a radix

Full Coverage

19 endpoints.
Everything you need.

From basic natal chart calculation through to complex predictive techniques, lunation finding, and ephemeris generation. All responses are JSON with consistent error shapes and HTTP status codes.

Built on
Swiss Ephemeris Astrodienst AG — industry standard
15 House Systems Placidus to Gauquelin
Geocentric & Heliocentric Dual reference frame
Newton's Method Precise event finding
Fernet Encryption AES-128 key storage

Free & Open Source

AGPL v3 licensed.
Run your own instance.

ephemeralREST is released under the GNU Affero General Public License v3 (AGPL v3) to maintain licensing compatibility with the Swiss Ephemeris, which is itself AGPL v3. This live instance is free for all to use with no registration required for public endpoints.

Full source code, documentation, and setup instructions for running your own instance are available on GitHub — including the Flask API backend, this admin portal, and the Swiss Ephemeris data files.

⬡ View on GitHub API Documentation
License
GNU Affero General Public License v3
ephemeralREST uses the AGPL v3 to maintain compatibility with the Swiss Ephemeris. The AGPL v3 requires that source code be made available to anyone who uses the software over a network.
This Instance
Live & Free to Use
No cost for public endpoints. Register a domain or user key to access authenticated endpoints and predictive techniques.
Backend
Flask · SQLite · Python
Lightweight, self-hosted. Runs on any Linux server with Python 3.10+. Swiss Ephemeris data files included.

API Access

One key.
Everything unlocked.

A single API key gives you full access to all endpoints — chart calculation, predictive techniques, ephemeris data, lunations, and apsides.

Keys are free for development and low-volume personal use. No tiers, no paywalls, no credit card. If you need higher limits for production traffic, just mention it in your request.

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Building an application
Chart calculation, progressions, returns — everything you need for an astrology app.
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Research and data work
Monthly ephemeris, event finders, and bulk access to planetary position data.
◆
Personal projects
Use * as your domain for direct access without needing a website or server.
○
Evaluating the API
Request a key and start building immediately — your key arrives by email.
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Free Access

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