I finally bit the bullet and bought a semi decent lens for my 450d, a Sigma 50mm f1.4. I got the sigma over the canon lens as you can use the clip in LPR filters in the camera plus it was a bit cheaper..
I have only taken a few shots with it at night with the moon almost full. There is quite a bit of chromatic aberration when set at f1.4. Guess I need to stop it down a bit. Has anyone used one of these lenses for star shots?
The Lord giveth, the Revenue taketh away. (John 1:16)
  