This is really neat. Now, I don't have a lot of personal experience with light from that size of moon, but I do know that water has many faces. This means the light wouldn't be as spread, but more broken among darker spots of water. Another thing you could consider is tightening up some of the edges of the buildings off to the left.
Cool composition. Nice magical moonlight colors!! Besides working out the details I feel like the planet on the left could use a little bit of personality like the big one. Also maybe the shapes of the buildings could be used to say something a bit more? Play with the shapes/windows to be more deliberate maybe.
The mood of the piece is very interesting and the right side of the piece is really nice. I think it could be improved by tightening up the left side, especially the buildings. Having some more interesting silhouettes would help the interest a lot.