Ok, so this is my first credible peice of work in photoshop, and I am really happy with the outcome. CnC is welcome, encouraged, all that stuff. Tear it apart. This is my first real peace of work, and I'm happy with the result.
It looks pretty cool. One of my concerns would be that you can see the stars through the planet. If you think about it, when you see planet with a shadow, it still would retain its shape, you wouldn't see stars in the shadowed area. So it should still be circular with a void in the star field. (I'm having a bit of trouble describing it, I hope you get what I"m trying to get across.....) Kind of like this picture. I'm not sure what the thing is on the left, but another thing you may want to address is the star field. It is a little bland. I couldn't tell you how to improve it other than check out some tutorials since I myself am terrible and making star fields :S . Well, keep up the good work.
Ok, I'll edit and add more to the starfield. Maybe some space dust or nebulas or something? And fix the planet stars