Collimation with Glatter Laser: 2" or 1.25" plus Parallizer?

[opticalpath]

I want to use a Howie Glatter laser to assist with some steps in collimating a Mak-Newt (fitted with a Moonlite focuser).  My first thought was that the 2" barrel laser would provide more accuracy of fit than the 1.25" model in an adapter.  However, given the importance of parallelism, even more than concentricity, would it actually be better to use the 1.25" barrel model in conjunction with a Glatter Parallizer ...... since this combination would remove any residual error caused by the 2" focuser clamp ring?

Adrian

[bambuko]

Yes, I would use the parralizer (with 1.25" laser), since as you say it eliminates the errors.

[Howie Glatter]

Adrian said "would it actually be better to use the 1.25" barrel model in conjunction with a Glatter Parallizer"

  Yes, because it would prevent  misalignment if there was a sloppy fit in the 2" drawtube. That said, Ron at Moonlight produces close tolerance drawtubes, so the fit and alignment of my 2" would be pretty good.

[laser_jock99]

I went for the 2" on the basis that any other insert might induce further concentricity errors + all my scopes have 2" (or larger) focussers anyway!

[Howie Glatter]

" I went for the 2" on the basis that any other insert might induce further concentricity errors"

You are correct that each additional interface will cause an additional radial offset (concentricity) error, but if you use a Parallizer adapter, the twp offsets are in opposite directions, so they tend to cancel. The offset (decentering) error is usually inconsequential; it is the tip and tilt efrror that increases with distance, which is of consequence.

[opticalpath]

Thanks for the advice about this.  All my scopes have 2" focusers too, but certainly not all the drawtubes are quite as well engineered as the Moonlite.  So it seems to me that the 1.25" (or 1.25"/ 2") unit in combination with the parallizer is indeed a better choice, since it is likely to give at least as good an alignment of the laser as the 2", in *any* focuser.

Adrian