Astronomy MCP Server

Astronomical catalog data and observing session planner. 13,000+ objects from OpenNGC. Exposed over MCP by the astronomy mcp server, that capability becomes something an assistant can invoke while it works, not something you go and do afterwards.

What it actually does

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

Adding it to your client

The server ships on npm as astronomy-oracle, so your MCP client can launch it on demand — there is no separate build step. Add the server block to your client's configuration, restart it, and the tools register themselves.

Its toolset

Everything the assistant can do here goes through one of these:

• Source — License
• lookup_object — Look up a celestial object by Messier number, NGC/IC designation, or common name. Optionally compute visibility from a given location and time
• search_objects — Search and filter the catalog by type, constellation, magnitude range, angular size, or catalog membership
• plan_session — Generate an observing session plan for a given location and date. Returns the best objects to observe grouped by time window

Caveats

• It runs with your machine's permissions. That is convenient and also the reason to think about what you point it at before you approve a tool call.
• MCP clients confirm each tool call by default. Leave that on until you have watched what the astronomy mcp server does with a few real requests.

When to reach for it

This sits in the developer tooling group, where several servers overlap in what they claim to do but differ sharply once you actually set them up. Astronomy's toolset — Source, lookup_object, search_objects and 1 more — is a fair guide to whether it matches your workflow. It is maintained by gregario; worth a glance at recent repository activity before you build anything load-bearing on it.

We check each listing at SyncDev against the project's documentation before it goes live — if something here drifts out of date, it is a bug worth reporting.