[Steffen]

You should easily be able to see the remaining one of the equatorial bands with an 8" Dob. If you don't then that could be because the seeing is bad (not much magnification possible) or because the scope is out of collimation. The second band has gone "missing", and the GRS isn't as spectacular as in the early 90s for example. With a well-collimated 8" Dob you should be able to see finer details nevertheless, but it varies a lot with the conditions.

Jupiter will come into better view in a few months time. Right now it's -2.4mag and 38" wide, but in September it'll be -2.9mag and 50". It will also be up all night and therefore easier to observe.

Cheers
Steffen.