Anyone use this lens for Astrophotography? How is it in the corners, is there too much coma? After buying the 35/2 IS, I gotta say I am most impressed by that line of Canon EF primes in terms of IQ and build quality. Brian Carnathan gave the 24 a pretty good review, but I'd be particularly interested in it's ability to capture Milky Way shots and stuff like that. Anyone with some experience with this lens in those situations?