[GraemeT (Graeme)]

I have a new Skywatcher 8" collapsible Dob with a max useable magnification of 406X. I purchased a 3.2 TMB Planetary eyepiece in the hope of seeing some detail on Jupiter. This morning had the first clear skies since the eyepiece arrived and the view was less than startling! The calcs gave a magnification of 375X but the image was fuzzy to useless.
Is this due to 1. the magnification limitations of the scope, 2. poor collimation ( I thought I had done a pretty good job using the tutorial on this site), 3. something else I haven't thought of , or 4. a crook eyepiece?
Cheers
Graeme