The moon, like the sun, subtends an angle of 1/2 degree and is so far away that it might as well be infinite. In other words, use an infinite light with a .5 degree shadow blur radius.

Unless you simulate a long-exposure image (where night turns to day) the sky contributes nothing of importance to the lighting, so it doesn't matter what you use for celestial object (stars, planets, the moon) representation.

A proper (and I mean proper with 10000:1 contrast) HDR image of the sky (with moon in it) would take care of itself for sharp shadows, but I have never seen any such thing ever published. Maybe from Dosch. But most "HDR" images are nothing of the sort.

LDR images are limited to a dynamic range of 255:1. HDR can (and should) be 10000:1 with the sun or moon in them, but the most I've seen is around 1000:1. This is because photographers don't know what we need for HDR in CG. They're just doing it for reasons I don't understand.

So - add an infinite light and call it done.

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There is also the never ending debate about color. Moon light is the same color as sun light. This means slightly yellow. But perception using our night vision (rods versus cones) gives it a blue tint. Cameras also pick up the blue a bit more. Some purists argue it's not about perception, but actual color. Other purists argue it's not about actual color, but perception. Personally, a little extra blue makes it more real. Perfect? No. I am tired, though, of the endless inability of some people to grasp the not-so-subtle distinction between these two words: better, perfect.

Do what you like - not what other people like. I hope you find this info useful, if not definitive.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)