If you want to make a realistic atmosphere, I think the gradient would have to be a lot sharper, with a bright layer close to the surface and a sharp decline to dark blue or purple going out. I just looked at google for images of the upper atmosphere to see if the stars can be seen through. It looks like stars appear a lot more faded on real pictures, especially with the light from Earth taking most of the light balance in the image. You can hardly see stars at all on these pictures.

• agiel - www.linfa.net