For your ground fog, try a volumetric slab (ALT-click the infinite plane on the create menu). Try the material 'Summer Soldier Slab Clouds' (Volume materials -> top row, fourth from the left). Manually place your moon where you want it in your scene. Hold down CTRL and double-click the sun trackball on the Sky & Fog menu. Then hold down SHIFT+ALT+CTRL and click in your scene window where you want the moon (just CTRL+ALT+click for the sun). You will see a blue (yellow for the sun) star appear in your scene that represents the moon. Stars..... hmmm.... dunno 'bout stars. Try lowering the haze to make your stars brighter. Oh, and they only show up at night. ;)