Astronomy Oracle

What gregario/astronomy-oracle MCP server does

The gregario/astronomy-oracle MCP server gives MCP clients access to a bundled catalog of more than 13,000 deep-sky objects. The catalog includes NGC, IC, Messier, and addendum entries sourced from OpenNGC. Agents can retrieve object facts, find objects that meet observational filters, or generate a plan for a night at a specified location.

Object records can include the object type, right ascension and declination, magnitude, angular dimensions, surface brightness, Hubble type, and catalog cross-references. When a latitude, longitude, and time are supplied, lookup can also return altitude, azimuth, and rise, transit, and set times.

How it works

All catalog data is packaged with the application, and the astronomy calculations run locally. The implementation calculates Julian dates and sidereal time, then uses those values for altitude/azimuth conversion and visibility timing. The gregario/astronomy-oracle MCP server therefore does not need a network connection or an external astronomy API at runtime.

Session planning evaluates objects for a supplied date and location. Results are divided into evening, midnight, and pre-dawn windows, with observability scores based on factors including altitude, magnitude, and angular size. The output is intended to help an agent select targets for a particular observing session rather than merely retrieve catalog rows.

Setup and configuration

Run the server directly with:

npx -y astronomy-oracle

The package can also be installed globally with npm. The documented Claude Desktop configuration starts npx with the -y flag and the astronomy-oracle package. The README identifies Node.js 18 or newer as a requirement. No credentials or environment variables are documented.

The repository also documents a Claude Code command using the same npx invocation. Development instructions include separate commands for tests, building, development mode, and the MCP Inspector, but those are not required for normal use.

Tools and capabilities

• lookup_object accepts a Messier identifier, NGC or IC designation, or common name. Optional location and date arguments enable visibility calculations.
• search_objects filters the catalog by object type, constellation, magnitude, angular size, or catalog membership. Matching results are returned in a brightness-sorted table.
• plan_session accepts a location and date and can apply minimum-altitude, maximum-magnitude, and object-type constraints. It returns targets grouped by evening, midnight, and pre-dawn periods.

Limitations and notes

The catalog is focused on deep-sky objects rather than a general-purpose ephemeris or live observing service. Calculations and catalog content are local, so the server does not fetch updated data from the network. The bundled OpenNGC data is distributed under CC-BY-SA 4.0, while the application code is licensed under MIT. The gregario/astronomy-oracle MCP server is best suited to catalog-backed lookup and planning workflows where those data sources and deterministic local calculations are sufficient.