Good work! :-)

Maybe you could lower the contrast between the black and white parts of the moon. This could be done in several ways, like for example attaching a brightness/contrast filter node to the image in the function editor or adjusting levels of the moon bitmap in photoshop prior to loading it in Vue.

Another thing: don't forget that the real moon always shows the same face to the Earth but with this method, the image that faces the camera only coincidentaly is that same face that we are all used to. If it's not, the viewer won't immediately realize what's wrong with the moon but he/she will know that there's something wrong, and this will have a negative effect on perceived realism.
So, I would advise that you check reference images and try to rotate the sphere until the image that faces the camera is the familiar one.