Gosh!! how did you got that atmosphere effect?? looks awesome!
The atmosphere effect I used comes in two parts, both are actually quite simple.
To make the atmospheric "ring", use alpha-to-selection on the planet layer (after mapping it to sphere) to select it, then switch to the new layer, fill the selection with the desired atmosphere color, deselect and blur it a little bit. Then reselect the same region as before and erase, and you've got just the ring. You'll also need to erase the section over the darkside, unless the atmosphere has its own lighting effect in which case you can do something different for it.
The haze effect is made through the exact same method, except with inverting the selected area. This way when you blur it, it spills onto the planet instead of into space. This technique is not as realistic as actually rendering the atmosphere in a 3D program, but the effect is still pretty convincing I think.
Turnsky: Nice image, very atmospheric. Do you mind if I ask how you made those rings? They're really good.
