Focus Focus Focus
Oh, and up your ISO somewhat. I happened to be playing with my 5DMkII on a Star Adventurer with 100-400 L series lens at 200mm, iso 6400 and single 30 second exposure. It is a bit noisy, but there is still a lot of data in there.
Your lens may be introducing some other aberrations of course, I assume the image is cropped so we may be seeing coma and chromatic issues, especially if it is off centre, but make sure you get a really perfect focus before worrying about anything else.
LOL, this time with the correct image!