i think the transition from day to night should be thinner, not as wide:
http://www.photoshop-weblog.de/images_articles/planet-tutorial.jpg

though, when I think about it... it does take a while to get light in the morning. so I would've made the transition rather slow as well, if I hadn't seen planet pictures.

other than that, great work smile


~"I never let school interfere with my education"~
-Mark Twain