SkyMar

Marine Celestial Navigation

A celestial-navigation instrument that speaks the Nautical Almanac's language. Real-time sky, sight planning, intercept-method sight reduction, fully offline, on your phone.

Download for Android

Validated against official astronomical references

v1.1.0 · Free · French interface · Android 7+ · No ads, no tracking

Real-time sky

The sky as a navigator sees it

Not a generic planetarium, SkyMar highlights what matters on the bridge wing. The 57 selected stars and Polaris are labelled with their SHA and declination of date. Constellations, the Milky Way, and a brass compass rose orient you at a glance.

Drag to pan, pinch to zoom, with kinetic inertia
Nautical-twilight sight window for your position
Best 3 to 4 stars for the strongest fix
Tap a star for its full almanac data

Sight reduction

From sextant to position

The full intercept method: sextant corrections (dip, refraction, semi-diameter, parallax), computed altitude and azimuth, and a least-squares fix from the lines of position, simultaneous or running.

Special sights

Noon sight, Polaris, compass error

Meridian passage for latitude and longitude, latitude by Polaris, compass error by azimuth or amplitude. WMM 2025 magnetic variation computed on device.

Direct updates

Keep SkyMar up to date

Check for releases from Settings and download updates directly from slmar.co. SkyMar verifies the download before opening Android’s installer. All astronomical calculations work offline.

Fully offline

Calculate without a connection

No account or analytics. Position is computed on-device and never transmitted. Works at sea with no connectivity, the way a navigation instrument should.

Built by a mariner, for mariners

Designed by a serving master mariner with a quantitative background. Not a generic planetarium with nautical paint, an instrument that speaks the language of the watch.

Download for Android

Free · Offline · No tracking · No ads