Refractor Collimation Problem....How do you solve t

Hello,

I'm feeling fairly frustrated. I'm in the process of rebuilding a 5" F15 refractor that I built up back in the mid 70s...Jaeger lens (and a good one at that!). I decided that my original large Unitron focuser was not up to the task anymore particularly since there was no way to secure heavy items in the draw tube attachment since there is no clamping mechanism, just slide in pressure. So I bought a really beautiful 2" focuser from Moonlite, that comes with a 1.25" adapter ring. Also have a 1.25" adapter ring from Williams Optics.

Problems start immediately when I have tried to use my 1.25" laser just to align the focuser with the center of the lens (never mind the cell alignment). The adapters fit so loosely into the 2" focuser that tightening the set screws, either to hold the adapter, or to tighten the 1.25" side around the laser, cause the alignment to the center spot to shift quite a lot from test to test. (The beam swings at least 3/8" around center.) I wrote to Ron Newman at Moonlite about this and got a swift response that "all" adapters are made to fit pretty loose, and that I ought to use a 2" laser with no adapter to align. Fine, I can accept that as reality, but why bother? It just means that anytime I would use any equipment, in any adapter...even a precision Williams 2" diagonal, or a 1.25" binoviewer, camera, I might as well have not bothered with the alignment! Most all of my equipment is 1.25" What does a person do here? I've thought of going to a machine shop and having a "tight" fitting 2" to 1.25" adapter made; at least if I had that adapter, and aligned with it, I could be sure of keeping some alignment. Or am I being overly fussy here? How do you all deal with this issue?
Sorry if this is old material...I'm kind of new here.

What laser collimator are you using?? Good ones like Howie Glatter's are carefully machined to fit nicely in the adapter but the imported ones seem pretty sloppy.

Also, I think a chesire is the tool of choise for collimating a refractor.. But i could be wrong...

Jon

Hi Peter
You can use simple Scotch Tape to snug the adapter to the ID of the focuser tube. Usually one wrap all the way around will usually be enough, don't overlap. Then do the same for the laser or if the adapter has the brass ring inside just barely tighten the screw so the laser can still turn. Once you get a snug but not tight fit you need to unsert the laser without tightening and lightly push it flush to the face of the adapter and rotate it to see if the laser is well collimated. If you haven't checked laser collimation nothing is going to matter. I've tried 2 Lasermates and both were badly out of collimation. My Howie Glatter is dead on and has stayed that way for a few years now. Once you get the slop out and sure the laser is collimated then you are ready to check and adjust the focuser collimation.
Hope this helps
Buck