It seems the sun actually shines light on the background, and if you want to do something like add a star field on the background, the sun influences the color and brightness of the stars. Is there a way to prevent all lighting on specific surfaces?
Sounds like you have colour enabled for your surface layer or whatever you're doing. You want to use no colour (unchecked) and use the luminosity function. If you are using a default shader, make the colour absolute black (0) and then, again, use the luminosity function. I haven't experienced what you are talking about except with actual colour on the background sphere is above 0.
If all else fails you could use a default shader, and luminosity, in addition use a scalar to boolean (on same star mask for luminosity), and input into the opacity function. Then the background sphere won't be visible altogether except where stars are.
Removing the color did the trick! Thanks!