I would use a spotlight to create the light source for your moon. I have a tutorial here that explains how to enhance the light in a scene. It would work just as easily for a night scene although you may wish to reduce the brightness of the spotlight.

http://www.renderosity.com/mod/tutorial/index.php?tutorial_id=2281

I find that when working with Bryce you can get some great results from the skylab but at the expense of illuminating your scene correctly. I'm going to have a play with Bryce and see if I can replicate the image then I'll share the results with you.

 

http://joevinton.blogspot.com/