@pipeworx/usno-astronomy

Solar eclipses, local eclipse circumstances, Moon phases and the seasons from the US Naval Observatory's Astronomical Applications API. Answers "when is the next solar eclipse", "what time does the eclipse start in Madrid", "when is the next full moon" and "when is the summer solstice" from the official ephemeris.

Part of Pipeworx — an MCP gateway connecting AI agents to 1556+ live data sources.

Tools

• usno_solar_eclipses(year?) — the solar eclipses in a year with date and type (total, annular, partial, hybrid). With no arguments it returns the next eclipse after today. Lunar eclipses are not published by this API.

• usno_eclipse_circumstances(date, lat, lon, height?) — what a solar eclipse looks like from one place: magnitude, obscuration, duration, and the UT time, Sun altitude and azimuth of each contact. found:false with reason:"not_visible" when the eclipse cannot be seen from there.

• usno_moon_phases(year? | date?, count?) — every New Moon, First Quarter, Full Moon and Last Quarter in a year, or the next count phases from a date, plus next_full_moon / next_new_moon.

• usno_seasons(year?) — equinoxes, solstices, perihelion and aphelion for a year, with northern-hemisphere season names attached.

Related MCP server: astronomy-mcp-server

Auth

Keyless.

Data sources

• https://aa.usno.navy.mil/api/eclipses/solar/year?year=2026 — solar eclipses in a year.

• https://aa.usno.navy.mil/api/eclipses/solar/date?date=2026-08-12&coords=40.42,-3.70&height=0 — local circumstances.

• https://aa.usno.navy.mil/api/moon/phases/year?year=2026 and /api/moon/phases/date?date=YYYY-MM-DD&nump=N — Moon phases.

• https://aa.usno.navy.mil/api/seasons?year=2026 — seasons.

Things the next person would otherwise rediscover:

• All times are UT1, never local. Every response carries time_note.

• Years are limited to 1800–2050; USNO refuses others with an HTTP 200 whose body is {"error": ...}. Every error, including "eclipse not visible from selected location", comes back as 200 + error, so the pack reads the body rather than the status.

• height must be an integer number of metres; a decimal is rejected.

• The loc= place-name form of the circumstances endpoint answers "Please supply valid coordinates" — pass coords=lat,lon and resolve place names first.

• There is no lunar eclipse endpoint (/api/eclipses/lunar/* is 404).

• USNO's front end can take 3 s to accept a TCP connection and 6 s more for TLS (measured 2026-09-10, 6–22 s per call). The gateway caches this pack's answers for a week, which is honest for a fixed ephemeris.

Quick Start

Add to your MCP client (Claude Desktop, Cursor, Windsurf, etc.):

{
  "mcpServers": {
    "usno-astronomy": {
      "url": "https://gateway.pipeworx.io/usno-astronomy/mcp"
    }
  }
}

What this endpoint actually serves

tools/list at https://gateway.pipeworx.io/usno-astronomy/mcp returns the tools in the table above plus the shared Pipeworx meta-tools — ask_pipeworx, discover_tools, search_within, remember/recall and the rest of the gateway-wide set. So the tool count you see is larger than this table: a single-pack endpoint currently lists roughly 30 shared tools alongside the pack's own. The connection's initialize response states its exact scope, and is the authoritative answer for a given day.

This is deliberate, not multiplexing by accident. The meta-tools are what let a scoped connection answer a question this pack does not cover — via ask_pipeworx, which routes across the whole catalog — without you adding a second MCP server. There is currently no way to mount a pack endpoint without them; if the extra schemas cost you more context than the routing is worth, connect to the full gateway once rather than to several pack endpoints.

Or connect to the full Pipeworx gateway to get every pack's tools listed directly, instead of just this one's:

{
  "mcpServers": {
    "pipeworx": {
      "url": "https://gateway.pipeworx.io/mcp"
    }
  }
}

Both URLs reach the same gateway and the same 1556+ data sources. The only difference is which pack's tools are listed directly; ask_pipeworx reaches all of them from either one.

Standalone (no gateway account)

This package also runs as a local stdio MCP server — no Pipeworx account, no gateway round-trip:

{
  "mcpServers": {
    "usno-astronomy": {
      "command": "npx",
      "args": ["-y", "@pipeworx/mcp-usno-astronomy"]
    }
  }
}

Or run it directly to confirm it starts:

npx -y @pipeworx/mcp-usno-astronomy

It speaks MCP over stdin/stdout and answers initialize/tools/list/tools/call for only this pack's tools — none of the shared meta-tools the gateway connection above adds. Same source, same tools, no ask_pipeworx routing.

Using with ask_pipeworx

Instead of calling tools directly, you can ask questions in plain English — this works on the pack endpoint above as well as on the full gateway:

ask_pipeworx({ question: "your question about Usno Astronomy data" })

The gateway picks the right tool and fills the arguments automatically.

More

• Docs and guides

• pipeworx.io

License

MIT