Another excellent way to get a nice crescent shaped moon/planet is to change the shot camera you use in Part 1 to a 200 mm camera (and then adjust the Y position to again make sure the planet fills the rendering space appropriately).
Rendering realistic crescents (and actually, just more realistic everything) will be a lot easier.
If you REALLY want to go crazy, you can set up the scene with only the moons you want and a starmap ONLY (no atmosphere, just outer black space and moons) (Ok, I will plug Digital Carvers Guild Starbrigh plugin here which ROCKS!). Insert a spherical camera and render the scene with a pretty big resolution (like 10,000 x 10,000 pixels).
You can then insert a sphere into your scene, drop that GIGANTIC render into the glow channel, make the sphere completely transparent and use it as a star/moon backdrop. It's a little more difficult to manage when rotating it but it works.
Why would you do that? Because you can go in with an editor and edit out those pesky stars that are overlapping your moons and get the darn thing to look correct.