3D moon phase simulator: tonight’s phase from where you are

Source on GitHub

Last Quarter · 50% lit

  · 388,838 km away

Last Quarter
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View from·west, 29° up

The moon as it looks right now, from where you are standing.

The sphere never turns. It holds still the way the real moon keeps one face to us, and only the sunlight moves around it. Which way the crescent leans depends on your latitude, so the view from Melbourne is not the view from London.

How the phase is calculated

Every view starts as a calculation, not a keyframe. The positions of the sun and moon are worked out for your latitude, longitude and the current minute, and a single light is placed from those numbers. Change the time and the shadow line moves because the geometry moved.

Why the moon looks upside down in the southern hemisphere

Southern observers look at the moon from the other side of the earth’s axis, so the lit edge appears rotated by roughly half a turn. A crescent that opens to the right in London opens to the left in Melbourne. That rotation is computed here from your own position, which is why picking a different city visibly tips the moon over.

The moon doesn’t rotate to make a phase

It is tidally locked, keeping one face toward earth. Nothing here spins to produce a phase; only the light moves, which is how phases actually happen. It also means the shadow line falls across real craters instead of across a texture that has been turned into position.

Where the surface comes from

Colour, relief and roughness maps from NASA’s Lunar Reconnaissance Orbiter. Drag anywhere to move through time.