[muench]

The distance from earth to the moon is 384,400 km, and in the smaller detail picture that earth to moon distance is about 23 pixels. Or about 16,700 km per pixel.

And note they describe that small picture as "zoomed in", So I figure 400km is about 23 or maybe 24 pixels at most =D (or a diameter of less than 50 pixels).

Waiting for someone to find an even better estimation!

[nomercy400]

You are overlooking one major thing: From the perspective of the camera, the position of the moon relative to the earth matters for the number of pixels. For example, if the moon was directly between the earth and the camera, the earth-to-moon distance in pixels would be 0, but the real distance would still be ~384.400km.

You cannot use the earth-to-moon distance, unless you also know the exact position of the camera, earth and moon in the 3D plane.