Hi  -  I have found an annoying problem with the Meade APO refractor which I now understand is not uncommon with scopes of this type using a Crayford focuser. The problem is that when the focuser lock knob is tightened there is a slight backward or forward movement of the focusser which is enough to spoil critical focusing adjustment. I now do not use this knob but just have the tension adjustment tighter (prior to fine focusing) to maintain focusing position during an imaging session. I would be interested in any comments.   Cheers Peter