This looks pretty good Nutter, however i would have loved a bigger version, i have seen that the original size is big so why such a small preview?
Okay here are some things i would like you to improve or atleast what i think can be improoved the stars its till look to much filter>noise like. Try doing more to them, one of the most maken mistakes in spaceart is the underestiment of a starfield. If the stars looks unreal the image itself tends to look so aswell. The starfield is to clustered together and you can see the places where you erased to get some flow into it and thats nice however you need to have some single stars and some cluster all in one so that it will seem realistic. sorry for my bad english havent used it for quite a while

The nebula thing looks pretty good actually, maybe a bit more depth in it would be nice, im looking forward to seeing more drawn stuff from you

Planet:
Did you use only one texture here? It looks a little boring the texture that is i think the atmosphere looks pretty good and the lightning and shadow over the planet looks good too.

Looking forward to seeing some more