Calculation methodology and data sources

Lunar position and phase

The browser uses SunCalc to calculate lunar azimuth, altitude, distance, illumination and phase from time and observer coordinates. Azimuth is clockwise from true north and altitude is measured from the astronomical horizon. A negative altitude means the Moon is geometrically below that horizon.

Moonrise, transit and moonset

Rise and set are calculated horizon crossings. Transit is refined by sampling the interval above the horizon and finding the highest altitude. Local terrain and buildings are not part of the astronomical horizon, so the first visible moment may be later.

Weather assessment

Open-Meteo cloud cover and precipitation forecasts are compared with lunar altitude at the same time. Forecasts are model estimates, not measurements at the observer’s exact point.

Known limits

• Phone compasses can drift near magnets and steel structures.
• Atmospheric refraction and the local skyline affect visibility near the horizon.
• Cloud layers, haze and light pollution may differ from a forecast grid.
• The service is not intended for navigation or safety-critical decisions.

SunCalc documentation · Open-Meteo documentation