Hi John,
Mine is the skywatcher 150mm (f=1000mm), pictured below. It does have a cover.
The collimation of mine was way off. But it was corrected on the weekend by someone who knows how to do it. With good seeing and checking the collimation against a star (all looked great with my 10mm EP) The Barlow still showed satrun out of focus.
I didn't think much of it as the dew was getting heavy and EP's foggin, etc so i just put it down to that.
Hopefully someone can explain.