Wobbley eyepiece holder

I spent the weekend making a and silicone collimatable platform for my Chinese helical focuser on my 8" aluminum tube Dob.
Last night I put my new Scope Stuff laser in the holder and let it shine down on the opposite tube wall to set the angle of the focuser. When I rotated the focuser, the laser dot moved about a 6mm dia circle. When I held the focuser still and rotated the laser in the 1 1/4" holder (with the screw snug but not tight,) the dot rotates about a circle that is 4mm dia.
This brings a whole 'nudder set of epistemological questions (how do we know what we think is true, is true?).
Re. the laser:
Is this true: if the laser is off center in it's holder, I may get its rear end adjusted to not rotate at 12" amay, but unless it is paraxial, it will be off at some further distance, nes pa?
How can I tell if it is paraxial?
Should I get it to be a nonrotating at the distance of twice my focal length and be happy?
Is that close enough to then use my new auto collimator?

Re. the focuser:
If it's out, I'm basically cooked, right? Is this a common problem with threaded helical focusers? I love the fineness of the adjustment, but I wonder why I'm going to allthe trouble of collimating when the eyepiece holder is wandering so for about in each revolution.

You can check the laser easily enough with a v-block and a wall about 10-15 feet away. Then you would rotate it and see if it make a circle. If it does then it needs to be collimated. After collimation you can test the focuser and laser again to see what error there is left.

dan coyle said:
Is this a common problem with threaded helical focusers?

I had this problem both with the original Teleport helical focuser and also with the Gary Wolanski unit that I replaced it with, although maybe not quite as bad as what you describe. Otherwise, I loved the Wolanski's fine focusing. It is not a problem with the Kineoptics HC-2 Helical Crayford ( http://www.kineoptics.com/HC-2.html ) that I use now, but the focus rate on it (0.75" per revolution) is just a bit too fast for my taste. Still, it'll have to do. For one reason or another, conventional focusers aren't a good option for either of my lightweight Newts with small secondary mirrors. I have the HC-1 ( http://www.kineoptics.com/HC-1.html ) on my little Newt and like it a lot (it does 0.5" per revolution).
--
Mike