I was out observing about a week and a half ago and the conditions were about the worst you could ever think of. The temp was about 30 (this is at about 9:30 - 10:00 at night!) the humidity must have been about 90% and the sky was covered in low rain clouds with a only small window of opportunity (break in the clouds) for viewing Saturn. It was that humid and hot that I was observing just in boxer shorts! (I was not in a public place) and I was still having to wipe my brow from sweat every couple of minutes. It was that hot that there was condensation on the bonnet of the car. Anyway even disregarding these conditions (and a very quick collimation using a film canister) the view of Saturn was surprisingly good. I could clearly see one of the belts in Saturn and the Cassini Division at about 140x. Anyway, I would focus on Saturn and then about a second or two later it would be out of focus again - it just wouldn't hold focus.
Is this what is referred to as focuser 'slop'?
Oh, the focuser is a stock 2 inch R&P. I know that the focuser was that great when I bought the scope and always had the intention of up-grading it.
Skywatcher (8 inch) focuser
I know. I've been there, done that. 
