Just received an 8" f/5 from Orion, and there's a little bit of space between the rings and the tube in some places.
I will call the screws to close the rings at 3 o'clock. At 3 and 9 o'clock things are flush, and at 6 and 12 things are not.
The maximum gap doesn't appear to be more than 1 mm.
I hesitate to tighten the rings much more because the tube already made a noise or two when I tightened the rings.
Is it normal for the rings not to be flush all the way around?