Moon Position Map

How it works

The moon’s ecliptic longitude, latitude and distance are computed in your browser from the truncated series in chapter 47 of Jean Meeus’s Astronomical Algorithms (60 longitude and distance terms, 45 latitude terms), which places the moon to within about 10 arcseconds. The sublunar point is its declination and the longitude where it is on the meridian; the visible hemisphere is the set of points where the moon is above a flat horizon, ignoring the small parallax and refraction shifts, which move the edge by less than a degree.

Illumination comes from the phase angle between the sun, moon and Earth using their true distances. Age is the time since the last new moon, found by iterating on the moon’s elongation from the sun.

Questions

Why is the moon sometimes up in the daytime?

The moon is above the horizon for about 12 hours in every 25, regardless of the sun. Only around full moon do those hours line up with the night. The map shows both the sun and moon overhead points, so you can see how far apart they are.

How far is the moon right now?

Between about 221,000 and 253,000 miles (356,000 to 407,000 km); the readout gives the value for the moment shown. The distance changes through each orbit because the orbit is an ellipse.

Does the map show moonrise and moonset times?

Not directly. The edge of the shaded area is the line of moonrise on one side and moonset on the other; scrub the slider until the edge crosses your location to read the time.