Good Good, atmosphere is a little glowy on the dark part, but overall it looks amazing, good app you got there mate 
Well, it's important to note that the viewpoint is only 1/2 the radius of the planet above the surface, so the visible portion of the surface isn't that big. So although the transition from light to dark may look like it's stretched wider than it ought to be, that might be in part because it's showing up that much bigger.
Blowfish has noticed there's some 'banding' going on in the dark area, which I've determined has to do with the way I'm discretizing the atmosphere. Increasing the minimum number of iterations might provide improvement, but it's the brute-force way to do it, and it seems to slow it down somewhat. That said, so do the normal maps, and the tangent-space math is probably wrong there anyway. Also I've got no texture-filtering, since it's all software and I haven't implemented anything like that. It would probably also make it slower.
If there's going to be much more discussion of this, I might have to start another thread in the programming board. Or be (voluntarily) thread-split. I reckon the images ought to remain here though.
