Sextant Navigation

Navigate by the stars. Learn celestial navigation from 15 stars, 4 instruments, and 6 real sight-reduction problems.

Sextant Navigation is a celestial navigation primer for sailors, students, and maritime enthusiasts who want to understand the ancient art of finding position by the stars.

The app covers the complete foundation of celestial navigation in three focused sections:

STARS — Browse 15 of the most important navigation stars used by mariners across the centuries, including Polaris, Sirius, Vega, Arcturus, Capella, Rigel, Procyon, Betelgeuse, Aldebaran, Antares, Spica, Fomalhaut, Deneb, Canopus, and Acrux. Each entry shows the star's constellation, apparent magnitude, and detailed notes on its navigation role — from Polaris as a direct latitude indicator in the Northern Hemisphere to Canopus and Acrux for Southern Hemisphere position work.

TOOLS — Learn how the four essential instruments of celestial navigation work: the sextant (measuring altitude above the horizon), the chronometer (providing accurate GMT for longitude), the Nautical Almanac (tabulating body positions for every hour of the year), and the plotting sheet (graphing lines of position to find the fix). Each entry explains both the theory and the practical steps of use.

PRACTICE — Work through six realistic sight-reduction problems, each with a named star, an observed altitude, a DR position, a step-by-step reduction showing index error, dip, refraction, GHA, declination, assumed position, computed altitude, and intercept, and a final position fix statement. Problems include a Polaris latitude shot, evening twilight fixes on Sirius and Vega, a dawn fix on Arcturus, a Southern Hemisphere Canopus sight, and a classic three-star fix using Rigel, Sirius, and Betelgeuse.

Everything works completely offline. No account required, no ads, no tracking.