I especially like the upper half. it actually looks like it depicts something. With the bright shining moon and birdlike creature flying in the dark night's rain... beautiful!
The lower half (about where the background becomes white-ish) doesn't really fit to the dark top. The nebulae (the black smokey stuff) give the top a good rounding but the white flares are just too bright. Also the tail of the bird looks like it was experiencing a lot of motion blur... (I hope you know which section i mean)
This could turn out really nice if you'd try to 'fix' the lower half. I mean it already looks great as it is, but I think these flaws should be bettered out.