Astronomy and Outdoor Tools
6 tools, free and without ads.
Tools that answer a question about where you are and what the sky is doing. Some compute from published astronomical models; others read the sensors already in your phone.
Both kinds need to know where you are, and neither sends it anywhere. Your location is used to compute an answer in the browser and is not transmitted, logged or retained.
Every tool in Space
Use your phone as a digital bubble level. Check if any surface is level or plumb using your device's accelerometer.
Live GPS coordinates, altitude, speed, and compass heading from your device.
Find upcoming solar and lunar eclipses with local visibility. See if an eclipse is visible from your location.
Moonrise, moonset, transit, phase, illumination and moon age for any location and date.
Tide times and heights for US coastal stations, with the full tide curve and the year's biggest tides.
Find Hohmann transfer windows between any two solar system bodies, with countdown, timetables, and ΔV estimates.
Computed, measured, and how much to trust each
Computed from a model — eclipse times, moonrise and moonset, tides, planetary launch windows. Orbital mechanics is predictable a long way out, so these stay accurate well beyond the present. The caveats are local rather than astronomical: a computed moonrise is the moment the moon crosses a flat horizon, which a hill or a building will delay.
Tides deserve their own warning — the astronomical part is exact, but real water level is also weather — pressure, wind and surge routinely move both the height and the timing. Treat a predicted tide as a plan, never as a safety margin, and check the local authority before anything where being wrong gets you cut off.
Measured by your device — the spirit level and the GPS compass read the accelerometer and magnetometer in your phone. Sensor tools are only as good as their calibration, and a magnetometer is affected by anything magnetic nearby: a phone case with a magnet, a car dashboard, a steel table. Calibrate, and cross-check against something you trust before relying on a bearing.
One consequence worth stating: an offline compass is genuinely useful in exactly the place a mapping app stops working. These load once and keep working with no signal.
Related categories
- Free Online Calculators — Sunrise and sunset times, and the time zone conversion an eclipse time needs.
- Health and Fitness Calculators — Pace and timing tools, for the run the tide chart is planning around.
- Games and Fun Tools — Natal charts — the same sky, a different set of claims about it.