Forgive me - I was raised in SCT land where backfocus is something that is taken for granted... So I got my first refractor - a 102mm f6. I love the views, but I didn't realize how much fiddling around I have to do to get different EPs to come to focus. I put in a short focal length EP - I have to put in an extension tube to bring it to focus. I switch to a long focal length plossl - I have to take out the extension tube. I use this same EP with a 1.25 prism diagonal to control scatter, I have to put the extension tube back in. The scope actually came with two extensions tubes... Is this something I just have to expect to deal with when using most refractors, or are some refractors more prone to this than others? I don't see this kind of thing usually discussed in product descriptions, but if one scope said "can reach focus for most eyepieces without having to use extension tubes", I would consider that a huge plus...