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Celestial Query & Calculation
Moon Phase Calculator
Query moon phase, lunar age and illumination for any date.
Try the tool
Phase: Waning Gibbous
Illumination: 94.8%
Lunar age: 16.94 days (of 29.53)
Tool principle
Uses the mean synodic month (29.530588853 days) referenced to a known new-moon epoch (JD 2451549.5). Illumination fraction is derived from the cosine of the phase angle (2Ο Β· age / synodic period), giving the fraction of the visible disc lit by the Sun.
Data source: Native algorithm β no API required.
User guide
- 1Pick any date using the date picker.
- 2Read the phase name, illumination percentage and lunar age (0 = new, ~14.77 = full).
- 3The disc preview shows the illuminated fraction and whether the Moon is waxing or waning.
Frequently asked questions
How accurate is this?οΌ
Within a few percent of published values β sufficient for planning observation nights and photography.
Can I query historical dates?οΌ
Yes, any date the browser accepts is valid.