The concept is great, the brush work and the roids are very nicely done. The planets multitude of textures is also a great touch. But the two biggest things that really put me off is, 1. The flare is very ugly, those lines just dont work in any picture. Try using an Axion filter. 2. The large comet needs some work. I know its not easy to create them, i've tried before, though i had a lot more luck doing one in terragen because of the different textures you can apply bit by bit. The comet kinda looks like a gritty wave from the sea. Bad description i know lol, but its what i see.