About

Today’s Moon Phase is designed to give you professional-grade lunar information in a way that is clear and easy to use. We show you the Moon’s current phase and illumination, moonrise and moonset times, moon age and distance, altitude and azimuth, and even the Sun’s altitude for context.

1. How we calculate

Our calculations are based on standard astronomical algorithms, consistent with the models used by institutions such as NASA and the U.S. Naval Observatory (USNO).

  • Positions and phases: We calculate the exact positions of the Sun and Moon using precise astronomical models, accurate to about one arcminute (1/60 of a degree).
  • Rise and set times: We compute moonrise and moonset with corrections for atmospheric refraction and the Moon’s apparent size, ensuring results match what you actually see from the ground.

2. Accuracy and limits

We put accuracy first, but it’s important to know the limits:

  • Atmosphere matters: Local weather conditions affect refraction, which can shift observed rise/set times by a few minutes.
  • Near the horizon: Because the Moon rises and sets at a shallow angle, even small changes in conditions can make the timing vary.
  • Location detail: Map position accuracy and your local horizon (mountains, trees, buildings) can also affect what you see.

3. Our rule of consistency

On most days, key values such as phase, illumination, distance, and age are calculated for local noon (12:00) in your time zone. On major phase days (New Moon, First Quarter, Full Moon, Last Quarter), the illumination values are shown for the exact moment the Moon reaches 0%, 50%, or 100%. Only on those dates do we use the actual event time for illumination, while all other values remain tied to local noon for consistency.

4. Why this matters

By combining scientifically validated methods with clear rules, our results closely match professional astronomical sources while remaining easy to understand. This way, you get information that is not only reliable but also practical for planning observations or simply following the Moon.