XT8 With good skys, Planets tend to be bright so can take powers to the maximum, very impotant for serious Martian observing... Do group viewings w/250X, needs correct placement so planet goes across the entire field of view, 200X is about minimum to see Martian details, need max for this tiny disc, have done 400X with best conditions but skys rarely allow... If you have trouble w/high powers, use lowest power eyepiece but leave things in-focus at highest power, if object is lost, simply switch to the lower eyepiece, center, and back to high power..you don't touch the scope during high power viewing until it move off the field....