I tried out the idea of using one sphere with fuzzy factor, then placing another sphere over it with shadow turned off and hard edges. It worked. Only bump I ran into is that the two sphere's can't be centered. The moon sphere with the cast shadow off is slightly in front of the other sphere with shadows and fuzzy on.

Ok, i see what you meant the first time. Still is a beautiful nice try. Would be better if you could put the first sphere a little bigger? I will see what i can do and post a message with an image. Maybe with two mind will get something good going. Later Eric. Pleiades