Course / Tools
Free celestial navigation tools
Calculators and instruments from the course, free to use in your browser. Each one shows its working, so you can check your own.
- Sight reduction calculatorHc, Zn and the intercept from your DR, GHA and declination, every step shown.
- Noon sight calculatorThe time of local noon, and your latitude from the Sun's noon altitude.
- Sun almanacThe Sun's GHA and declination for every hour of any date, 2026 to 2028.
- Polaris latitude calculatorLatitude from the Pole Star, with the a0, a1 and a2 corrections.
- Star finder (2102-D)A working 2102-D: the altitude and bearing of every navigational star at twilight.
- Work your own sightFrom the watch time and sextant reading to a plotted line, with the almanac built in.
- Celestial sphere explorerGHA, declination, LHA, altitude and azimuth on a sphere you can turn.
- Use Asterodos with your AIThe same tools as a connector for Claude and other assistants.
For learning celestial navigation, not for navigating: at sea, use the official Nautical Almanac and tables, and check every position by other means.