12 replies to this topic

[retroformat]

I haven't got much experience with laser collimation.  I'm shopping for a laser collimator (simple, slip in), and I have been wondering: how do I know, or how do I test, that the collimator itself is well collimated?   I am assuming that for it to work well, the laser collimator tube needs to be ideally co-axial with the laser beam coming out of it.  If the beam was off by a small angle, this would affect how you align the secondary mirror (to get the laser spot centered on the primary), and then wouldn't this screw up your telescope's collimation?  ... or at least it would affect the alignment of your focussing tube / eyepiece towards w.r.t. the optical axis, if your focusser has such alignment possible.

 

What experience have you had with laser collimators that do not work well, possibly for this reason that the beam is not co-axial with the tube of the collimator?

 

Are some brands of laser collimator more carefully built, better aligned than others?  They start out pretty cheap, and one would think spending more might get you more quality (but often this is not true).

 

Does it even matter?  Is my thinking incorrect about this?

 

Thanks

 

[Jon Isaacs]

You are thinking correctly.

 

In my opinion, the best laser collimators ever are the Howie Glatter collimators made by Howie himself before he passed away. 

 

Laser collimators are for Newtonians, you have an SCT and a Mak listed, do you have a Newtonian?

 

Jon

[CowTipton]

https://www.cloudyni...collimator-r509

 

The jig doesn't have to be that fancy.

You can use 4 nails hammered into a 2x4 creating two V shapes to seat your laser for example.

[JohnBear]

+1 for Cow!

Since you appear to only have folded optic (SCT & Mak-Cass) scopes you probably don't want to use a laser for collimation. See the links below for info.

 

http://karmalimbo.co...collimation.pdf

http://www.nightskyi...ollimation.htm 

 

Lasers are primarily used for collimating Newts.  One of the lesser known sinister laser collimation issues for Newts is that  if secondary mirror rotation is not "Spot On" a laser can provides a "false collimation" compensated-for-rotation result that is suboptimal.  .

Edited by JohnBear, 13 May 2022 - 10:24 AM.

[MellonLake]

Glatter and Farpoint lasers are excellent. These come very well internally collimated from the factory and include an aperture to make the beam a very small point with diffraction rings. The diffraction rings are very useful in collimating. These are quality products.

The cheap lasers with a target are often not internally collimated well and do not have the aperture. Also, Using the target with the reflected laser beam for alignment of the primary is not ideal. The beam in these collimators is large and oval which is not ideal. While they do have screws to collimated them internally, this is an annoying and troublesome process. These cheap lasers include Orion, SVBony, and all the laser sold on Amazon. I would not recommend a single laser sold on Amazon.

The Hotech collimators have a terrible centring system that makes accurate collimation nearly impossible.

Buy a Glatter or Farpoint if you want something reliable.

[Nemo51]

Well, there is always one: my 6 inch Tpo f4 newt is quickly and easily collimated with a second gen svbony, which almost always fully agrees with my Ocal collimation. Shocking, I know….

[MellonLake]

Well, there is always one: my 6 inch Tpo f4 newt is quickly and easily collimated with a second gen svbony, which almost always fully agrees with my Ocal collimation. Shocking, I know….

You must have got a good one.  

[SteveG]

I haven't got much experience with laser collimation.  I'm shopping for a laser collimator (simple, slip in), and I have been wondering: how do I know, or how do I test, that the collimator itself is well collimated?   I am assuming that for it to work well, the laser collimator tube needs to be ideally co-axial with the laser beam coming out of it.  If the beam was off by a small angle, this would affect how you align the secondary mirror (to get the laser spot centered on the primary), and then wouldn't this screw up your telescope's collimation?  ... or at least it would affect the alignment of your focussing tube / eyepiece towards w.r.t. the optical axis, if your focusser has such alignment possible.

 

What experience have you had with laser collimators that do not work well, possibly for this reason that the beam is not co-axial with the tube of the collimator?

 

Are some brands of laser collimator more carefully built, better aligned than others?  They start out pretty cheap, and one would think spending more might get you more quality (but often this is not true).

 

Does it even matter?  Is my thinking incorrect about this?

 

Thanks

Very simple. You place the laser in your focuser and slowly rotate it. If the beam spot on your mirror stays in place, the laser is collimated. If not, it will trace a circle.

 

The best buy for a quality laser is the dual 1.25/2” Farpoint. Mine fits perfectly in my focuser and is perfectly aligned. I also suggest the Farpoint cheshire. It will require you to place a new center marker on your mirror, but is worth it IMO.

https://www.adorama....rce=adl-gbase-o

[Speedy1985]

+1 on the 1.25/2" Farpoint laser and cheshire combo. I checked mine in a bench vise and the laser spot didn't budge over a 10' distance.

[luxo II]

Are some brands of laser collimator more carefully built, better aligned than others?  They start out pretty cheap, and one would think spending more might get you more quality (but often this is not true).

 

Does it even matter?  Is my thinking incorrect about this?

 

You're correct, it does matter - and a laser such as the Glatter laser collimator with concentric circle hologram is fine for collimating maks and SCTs, but overkill because the commercial varieties of SCT and maks only provide adjustment for 1 mirror, and that is best done with a star test - which is free and accurate.

 

Where the Glatter collimator is invaluable is with any Cassegrain that has separate adjustments for both mirrors as well as tilt adjustment for the focuser. For these a star test alone is not sufficient and you will need a Glatter or Hotech, or other bench test to align the primary mirror before aligning the secondary.

Edited by luxo II, 13 May 2022 - 06:12 PM.

[Nemo51]

You must have got a good one.  

And happy to have it-the Ocal is accurate, but far more involved. Then, there is the maddening video with quacking ducks and singing birds….

[retroformat]

Wow, thanks for all the replies!  I recently updated my profile, but I'm still a little new to this whole process, so I should have clarified that my use for a laser collimator would be on a truss tube Dob that I sometimes get to borrow, but which requires partial disassembly for transport - therefore it's always a complete start from zero with collimation.  I do have another topic running about collimating my Maksutov, so it is a topic of interest to me on several fronts!

I'm glad to learn that the laser collimators do come with adjustment.  I see the process would be not much different from aligning your polar finderscope (in an EQ mount polar axis); you rotate the laser collimator in some kind of fixture, and adjust to get the spot steady.

[SteveG]

Wow, thanks for all the replies!  I recently updated my profile, but I'm still a little new to this whole process, so I should have clarified that my use for a laser collimator would be on a truss tube Dob that I sometimes get to borrow, but which requires partial disassembly for transport - therefore it's always a complete start from zero with collimation.  I do have another topic running about collimating my Maksutov, so it is a topic of interest to me on several fronts!

I'm glad to learn that the laser collimators do come with adjustment.  I see the process would be not much different from aligning your polar finderscope (in an EQ mount polar axis); you rotate the laser collimator in some kind of fixture, and adjust to get the spot steady.

Don’t count on that to work. They don’t stay collimated, and their 1.25” barrels are undersized so they typically don’t register properly in a focuser tube. If you receive an uncollimated laser, return it.