Compositing, Layers, and other bits of confusion....

I’m trying to get my head wrapped around on how to use the compositing system in Blender. My scene is rather simple. It has a planet and a skydome. In the compositor, the planet has several adjustment nodes to increase blurriness, adjust RGB, etc., I’d like to have the background/skydome use different adjustments, but it’s all getting fed into the same render layers as the planet.

–How do I separate the background to make adjustments to it, but still have it feed into the final render? I though putting into its own render layer would help, but I’m not sure what’s happening…

–When I place the skydome into a separate layer, and though I have all the layers selected only the planet will render. I can only get the skydome to render with the planet if it resides in the same layer, but then it gets all the same adjustments, so…

–How can I separate my background from other elements so it doesn’t get affected by all the nodes that are affecting the planet (Blur, RGB curves, etc.,) but still make it into the final render?

~Chaz