Laser Collimation?

[ixian (Luke)]

I've seen a lot of posts on this forum and others dismissing laser collimation because the laser itself may not be collimated or because they don't compare to star test collimation. Assuming the laser is collimated, are they any good for quick and dirty collimation before a viewing session?

[Allan]

Good laser collimators are an in-valuable tool. They make collimating so much simpler and quicker to do. The Glatter collimators are the best and worth the price. At the very cheap end, as you mention, laser collimators introduce far more problems than they solve and are best avoided.

[Allan_L (Allan)]

Hotech, self centering collimator is a good mid price alternative.
Especially the new one with cross hair laser.
Few retailers in Aust, but worth the search.!!

In short, you get what you pay for.

[Steffen]

Collimation of laser collimators is easy to verify and fix if necessary. Also, given the small amount of play available in the draw tube, centring the laser collimator is not essential. Far more important is mounting it parallel to the optical path, since even a tiny angular error can have a noticeable effect on the outcome. Glatter makes a special 2"-1.25" adapter that ensures a parallel fit of 1.25" barrels in 2" draw tubes.

The actual issue with relying on laser collimators only is that you can mis-align the primary and still be able to contort the secondary into a position so that the laser spot returns to its origin. As the only source of truth a laser collimator is insufficient. However, if the position and rotation of the secondary is checked with a sight tube or one of those combined sight tube/cheshire/cross-hair tools then a laser collimator can get you close to very good collimation very fast.

Cheers
Steffen.

[ixian (Luke)]

Thanks for the info, very helpful.

[Jason D (Jason)]

Originally Posted by Steffen

The actual issue with relying on laser collimators only is that you can mis-align the primary and still be able to contort the secondary into a position so that the laser spot returns to its origin. As the only source of truth a laser collimator is insufficient. However, if the position and rotation of the secondary is checked with a sight tube or one of those combined sight tube/cheshire/cross-hair tools then a laser collimator can get you close to very good collimation very fast.

Cheers
Steffen.

That is untrue. If a quality laser beam hits the primary mirror center and retraces its path to the source then the primary mirror is aligned regardless of the secondary mirror position and rotation.

Jason

[Pinwheel (Doug)]

You need to check lasers are true regularly, I saw a great YouTube video making a laser collimator out of some PVC pipe 45 deg joiners. Brilliant idea & worked for me. Sorry I don't have the link but Google "Laser collimation".

[sn1987a (Barry)]

+1 on the Glatter. Buy the best, it'll last a lifetime. It's not a cost it's an investment that keeps paying off.

[PSALM19.1 (Shaun)]

Hi Luke,
I've always found that the laser collimation and star test are a pretty decent guide as to whether your scope is aligned or not...

[Howie Glatter]

Originally Posted by Pinwheel

You need to check lasers are true regularly, I saw a great YouTube video making a laser collimator out of some PVC pipe 45 deg joiners. Brilliant idea & worked for me. Sorry I don't have the link but Google "Laser collimation".

The only part of the laser collimator that should rest on the two "vees" of these test jigs is the cylindrical portion of the collimator that goes into the focuser. That is the only reference surface of the collimator. In most of the applications of this test that I have seen on-line, the back, non-reference end of the collimator sits on the test jig. If the collimator body is one piece, and was made on a lathe in one chucking (clamping), there is a chance the the back end will be concentric, but often this is not the case, and you will be miss-aligning your collimator with this procedure.

When I started making collimators I realized that if they are to be reliable reference and measurement tools over the long term, they needed to be highly shock-resistant. I developed methods of implementing this, and I shock test each one on three perpendicular axis.
The very few that I have gotten back for realignment had large bash marks, which was very gratifying.