Free · Find the horizon-light windows

Nautical Twilight Planner

Find when nautical twilight begins and ends before dawn and after dusk.

  • SunCalc 2 astronomy
  • Private in your browser
  • JSON and CSV downloads

Plan nautical twilight

Use the sample place or enter coordinates. All times use the chosen time zone.

1
Choose place and timeCoordinates stay on this device
2
Read the sky planToronto · America/Toronto
Your local result will appear hereUse the sample place, then press the gold button.

Three simple steps

How to use it

  1. Choose the date and coordinates.
  2. Read morning and evening windows.
  3. Treat the horizon as an open-sky estimate.

Your place stays on this device

SunCalc does the sky math inside this browser tab. Bookify does not upload or save coordinates, dates, or times. Results assume a clear, level horizon; terrain, weather, and buildings can change what you see.