Out of curiosity, you manipulated the skybox shader and replaced the black (sky) with blue? (and probably made the stars dimmer?)Photoshop let you add a nice gradient, which I'd love to be able to do via a shader, but it's not trivial. There is no atmosphere shader, just the skybox shader which is designed for space, so there's no easy way to orient a gradient with the horizon / sun (this would need to be done in the game engine). I could fake it for a still shot, but it would "fall apart" as soon as I start flying around.
But then again, I might be able to come up with something kinda clever - I haven't given up hope just yet! In the meantime, your effort was not in vain