Astronomy Oracle is an MCP server that provides accurate astronomical catalog data and observing tools for LLM assistants, eliminating hallucinated celestial data.
Look up celestial objects (lookup_object): Retrieve detailed data for any object by Messier number (e.g. M31), NGC/IC designation (e.g. NGC7000), or common name (e.g. Andromeda Galaxy). Returns type, RA/Dec coordinates, magnitude, angular size, surface brightness, Hubble type, and cross-references. Optionally provide latitude, longitude, and date/time to get altitude/azimuth and rise/transit/set times.
Search and filter the catalog (search_objects): Query 13,000+ deep-sky objects by type (Galaxy, Planetary Nebula, Open Cluster, etc.), constellation, magnitude range, angular size, or catalog membership (Messier, Caldwell, NGC, IC). Results are returned as a formatted table sorted by brightness (up to 100 results).
Plan observing sessions (plan_session): Generate an optimized observing plan for a specific location and date, filtering by minimum altitude, magnitude limit, and object types, with the best objects grouped into evening, midnight, and pre-dawn windows scored by observability.
Perform deterministic astronomy calculations: Compute Julian dates, sidereal time, and alt/az conversions — all processed locally without network dependencies.
Accurate astronomical catalog data and observing session planner for LLM assistants. Stops hallucinated magnitudes, coordinates, and visibility.
3 tools for object lookup, catalog search, and observing session planning
13,000+ deep-sky objects from the OpenNGC catalog (NGC, IC, Messier, and addendum objects)
Deterministic astronomy math — Julian dates, sidereal time, alt/az conversion, rise/transit/set times
Zero network dependency — all data is bundled, all calculations are local
Related MCP server: SkyQuery
Run directly with npx:
npx astronomy-oracleOr install globally:
npm install -g astronomy-oracleAdd to your claude_desktop_config.json:
{
"mcpServers": {
"astronomy-oracle": {
"command": "npx",
"args": ["-y", "astronomy-oracle"]
}
}
}claude mcp add astronomy-oracle -- npx -y astronomy-oraclelookup_objectLook up a celestial object by Messier number, NGC/IC designation, or common name. Optionally compute visibility from a given location and time.
{
"name": "lookup_object",
"arguments": {
"name": "M31",
"latitude": 51.5,
"longitude": -0.1,
"date": "2025-06-15T22:00:00Z"
}
}Returns detailed object data: type, coordinates (RA/Dec), magnitude, angular size, surface brightness, Hubble type, cross-references, and (when location is provided) current altitude/azimuth with rise/transit/set times.
search_objectsSearch and filter the catalog by type, constellation, magnitude range, angular size, or catalog membership.
{
"name": "search_objects",
"arguments": {
"type": "PN",
"constellation": "Lyr",
"maxMagnitude": 12.0,
"limit": 10
}
}Returns a formatted table of matching objects sorted by brightness. Supports filtering by object type (Galaxy, Planetary Nebula, Open Cluster, etc.), constellation, magnitude range, minimum angular size, and catalog (Messier, Caldwell, NGC, IC).
plan_sessionGenerate an observing session plan for a given location and date. Returns the best objects to observe grouped by time window.
{
"name": "plan_session",
"arguments": {
"latitude": 40.7,
"longitude": -74.0,
"date": "2025-03-20",
"minAltitude": 20,
"maxMagnitude": 10.0,
"types": ["G", "PN", "GCl"]
}
}Returns objects grouped into three windows (evening, midnight, pre-dawn), scored by observability based on altitude, magnitude, and angular size.
Source | License | Description |
CC-BY-SA 4.0 | NGC/IC/Messier catalog with coordinates, magnitudes, dimensions, and cross-references |
The OpenNGC data is included under the Creative Commons Attribution-ShareAlike 4.0 International License. See the OpenNGC repository for full attribution.
# Run tests
npm test
# Build
npm run build
# Run in development mode (tsx)
npm run dev
# Open MCP Inspector
npm run inspectMIT for code. CC-BY-SA 4.0 for OpenNGC data.
Look up a celestial object by Messier number (e.g. M31), NGC/IC designation (e.g. NGC7000), or common name (e.g. Andromeda Galaxy). Optionally compute visibility from a given location and time.
Inputs: name (required), date, latitude, longitude.
Generate an observing session plan for a given location and date. Returns the best celestial objects to observe grouped by time window (evening, midnight, pre-dawn), scored by observability.
Inputs: latitude (required), longitude (required), date, types, +2 more.
Search and filter the celestial object catalog by type, constellation, magnitude, angular size, or catalog membership. Returns a formatted table of matching objects sorted by brightness.
Inputs: type, limit, catalog, minSize, +3 more.
Recent tool additions, removals, and schema changes observed during successful MCP inspections.
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Scored across 3 tools
Each tool serves a distinct purpose: looking up a specific object, planning a session, and searching the catalog. No overlap or ambiguity.
All tool names follow a consistent verb_noun pattern (lookup_object, plan_session, search_objects) with underscores, making them predictable.
Three tools is well-scoped for a specialized astronomy server, covering the essential tasks without unnecessary complexity.
The set covers core use cases: object lookup, session planning, and catalog search. A minor gap might be detailed ephemeris calculations, but the surface is complete for its stated purpose.
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