io.github.cyanheads/astronomy-mcp-server

Search forward from a start time for the next occurrences of one sky-event class, selected by the `event` enum: solar_eclipse, lunar_eclipse, equinox, solstice, moon_quarter, opposition, conjunction, max_elongation, or perigee_apogee. Only solar_eclipse takes an observer: pass latitude and longitude to get local circumstances (contact times plus `local_visible`). Every other class is geocentric and needs no location — a lunar eclipse is the same event everywhere the Moon is up, so it returns contact times and no `local_visible`. The body-relative events (opposition, conjunction, max_elongation, perigee_apogee) require a `body`: opposition applies to the superior planets (mars through pluto), conjunction to any planet, max_elongation to mercury and venus, and perigee_apogee to the moon (perigee/apogee), earth, or a planet (perihelion/aphelion). Returns the next `count` occurrences (default 1). Start defaults to now; pass an IANA `timezone` for observer-local timestamps.

Report the Moon phase for an instant: illuminated fraction, phase name, synodic age in days since the new moon, phase angle, and the next four quarter phases (new, first quarter, full, last quarter) with timestamps. Answers "what is the moon phase tonight" and "when is the next full moon" in one call without iteration. The time defaults to now; pass an IANA `timezone` to also receive observer-local timestamps. The phase is geocentric — no observer location is needed.

Compute rise, set, and culmination (transit) times for a body at an observer location, plus the maximum altitude at culmination. For the Sun, also returns the three twilight pairs (civil −6°, nautical −12°, astronomical −18°) so a single call answers "when does the sun set and when is it truly dark." Searches forward from `start` (default today) and returns the next `count` cycles (default 1). Circumpolar or never-rises situations are reported as null rise/set fields with an explanatory note rather than an error — the fact is the answer. Default elevation is 0 m; pass an IANA `timezone` for observer-local times. This server does not geocode — resolve coordinates upstream first.

Compute the apparent topocentric position of one solar-system body (sun, moon, mercury through neptune, pluto) or a named bright star for an observer location and instant. Returns equatorial (RA/Dec), refraction-corrected horizontal (altitude/azimuth), and ecliptic coordinates, plus distance, apparent magnitude, angular diameter, phase angle, illuminated fraction, and the constellation it falls in. Positions are parallax- and aberration-corrected for the given observer; default elevation is 0 m and the default time is now. Supply `star` (e.g. "Sirius", "Polaris") instead of `body` to target a catalog star; `body` is ignored when `star` is set. Pass an IANA `timezone` to also receive the observer-local time. This server does not geocode — resolve a place name to latitude/longitude upstream first.

The one-call "what is up right now" answer. For an observer location and instant, iterate every naked-eye solar-system body (and, with include_stars, the bundled bright stars), compute altitude and azimuth, keep those above the horizon, rank them brightest-and-highest first, and attach a plain-language visibility note to each. The whole sky is gated by the Sun's altitude into daylight / civil / nautical / astronomical twilight / dark, returned alongside the list. `time` is a single evaluation instant, not a window — for "tonight" pass a time after astronomical dusk (use astronomy_get_rise_set on the sun to find it). Default elevation 0 m; use min_altitude to skip objects grazing the horizon. This server does not geocode — resolve coordinates upstream first; pass an IANA timezone for observer-local times on each body.