Very nice! I suggest you either get more foreground into the picture or remove the lower right black object. You want the viewer to believe they are either on the water (such as in a boat) or on land. You want your viewer to have a believable vantage point - on land would be a better choice. Also, I suggest you eliminate the small planet - it's not serving your image well because it detracts from the large planet, which is more than enough to suggest the location. (In real physics, being so close to one another, these planetary bodies would have long pulled themselves together from gravitational attraction). And lastly, you might want to thicken the clouds (which are excellent by the way) so that the stars are more obscured when behind the clouds (or dim the stars). I very much like how you under exposed the mountain range because they should only be a supporting element within the image. I like your work!
-Pat