⚠️ Informational use only — not for navigation or safety-of-life decisions. These sun, moon and twilight times are computed for convenience and are elevation-corrected, so they deliberately differ from the standard, level-horizon civil-twilight times that aviation and maritime regulators require. Do not use them for flight planning, to determine legal day/night or “lights-on” times, for navigation, or for any other safety-of-life purpose. Always verify against an official source. Safe use & disclaimers →

First light, last light,
and the twilight windows in between.

Civil and nautical twilight for any waypoint, with the moon phase and altitude that matter for tide planning. Same elevation-aware computation behind the marketing copy — works at any altitude, including inland reservoirs and high-mountain lakes.

Read the API docs See pricing

Civil twilight

Handy for planning around the “lights on” period; bright stars visible, horizon clearly defined. Note: the binding navigation-light times are sunset to sunrise under COLREGs / your maritime authority — not a computed twilight value.

Nautical twilight

The threshold beyond which celestial navigation becomes feasible. Sun centre at −6° to −12°.

Moon phase + tides

We are the tide source too: pair this response with our Tides API (FES2022) for high/low waters at any point — or use /v1/tides/window/ to get tide + light + moon in one call.

Pre-plan a passage

curl -H "Authorization: Bearer $THIRDTRAIL_KEY" \
  "https://thirdtrail.life/v1/ephemerides/?lat=49.5000&lon=-2.5333&days=7&tz=Europe/London"

Guernsey, week ahead. Returns sunrise/sunset, transit (solar noon), the four twilight phases, golden/blue hour, and the moon's rise/set/phase per day.

Push instead of poll

Subscribe to a webhook and get pinged 30 minutes before civil dusk at your next waypoint:

curl -X POST -H "Authorization: Bearer $KEY" \
     -H "Content-Type: application/json" \
     -d '{
       "event_type": "civil_dusk",
       "lat": 49.5, "lon": -2.5333,
       "callback_url": "https://yourapp.com/wh/twilight",
       "horizon_days": 30
     }' \
     "https://thirdtrail.life/v1/ephemerides/webhooks/"

Pro+ tier. We'll POST a HMAC-signed payload to your endpoint at the right moment, with retry-on-failure and a 5-minute operating budget. Full webhook contract in the docs.

Twilight conventions

Civil twilight: sun centre at −0.83° to −6°. Streetlights typically off; bright stars visible. Informational only — navigation-light timing is set by COLREGs / your maritime authority (sunset to sunrise), not by this value.
Nautical twilight: −6° to −12°. Horizon is distinguishable; navigation by stars is feasible.
Astronomical twilight: −12° to −18°. Faint celestial objects observable.

A null twilight value means the boundary was not crossed during the local day. Normal at high latitudes (e.g. Dublin from mid-May to late July, astronomical twilight does not occur).

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First light, last light,and the twilight windows in between.