laser collimator for telescope

[75RR]

I asked how to check the collimation on my Wild M8 and was told to use a "laser collimator for telescope"

Well I googled it and looked on Amazon and Ebay but I really have no idea as to which to get.
Looking for an accurate and economical one if that is not a contradiction in terms.

I know several members here have come in from the dark side and I was wondering if any of you remembered anything from your past lives. ;)

[JimT]

I am no help. In my "Dark Days" I would focus on a star and tweak the scope until I got concentric diffraction rings. Then I would not touch the adjustment screws again

JimT

[75RR]

... until I got concentric diffraction rings.

Suspect that is an "in" joke.

Sorry to hear that your telescope was un-collimated. ;)

[KurtM]

Main thing is to make sure the collimating tool is itself collimated. This is done by rotating the tool in an accurate holder (v-blocks), and checking whether the dot stays put or describes a circle. This implies, of course, that a means of adjusting the collimater tool is mandatory.

How will a laser collimator help align a stereo scope? And if the stereo scope turns out to be out of alignment, how will you align it?

Laser collimators for astronomy come in 1.25"/2" size to fit telescope focuser draw tubes. Any plan on how one might be used in a microscope?

Your eyes automatically compensate for quite a lot, as I'm sure you know. I can tell you from empirical observation that it's rare to see binoculars, as in field glasses, that are in good alignment out of the box when they're of the "consumer" price point category, and even more expensive ones bear checking before buying. But few people know anything about this (and indeed never even bother to learn what inter-ocular focus is for) and still get good use out of them. Good thing too, there's really no way mere mortals can collimate binos.

JimT is referring to the diffraction rings in the Airy disc. Beats the thunder out of me how anyone can collimate a telescope on a star image. No wonder he didn't want to mess with it any more! You can throw a star image out of focus and get a rough check on collimation by observing the position of the secondary mirror shadow position, but to actually make adjustments? Ouch, that sounds tedious at best...

[lorez]

I can share what B&L and Swift offered as alignment tools for their stereos, but it may not apply to the M8.

Let me know if there is any interest.

lorez

[75RR]

Hi Kurt,

How will a laser collimator help align a stereo scope? And if the stereo scope turns out to be out of alignment, how will you align it?

Have just asked this very question to the person that recommended I use a laser collimator to check the M8's collimation - should have asked before I suppose.
Have the service manual - the M8 is collimatable (is that a real word) though I am not sure it is something I really want to try.
Will let you know what he says.

[Crater Eddie]

Maybe I missed it somewhere, do you have reason to believe that the collimation is out?
CE

[KurtM]

Lorez, I'd certainly be interested in learning about it. Especially as I own both a B&L and Swift stereo scope.

75, I wouldn't touch collimation with a ten foot pole unless I really thought there was a problem with the image. But then, if it turns out to be not that bad to fix, I'd love to be corrected...

[75RR]

Thanks for the offer lorez, I have no idea if it is compatible.

Will see what he says. The laser collimator might just be one of the steps needed or might do it all.

[75RR]

Maybe I missed it somewhere, do you have reason to believe that the collimation is out?

Well, not sure what to say to that given my lack of experience with stereo microscopes but I feel a bit of eye strain after a bit and I find the viewing much more comfortable at lower magnification.
This is a stereoscope that was quite likely out in the field quite a bit, rattling around in a 4x4. Just wanted to check if it was me or the scope.

[KurtM]

Well, one way to get a rough idea is to "blink compare" the image. Focus on a specimen, then close one eye. Then switch eyes. Then repeat over and over. Almost every time in every instrument you'll get some image shift, but it should be relatively small. If it really jumps, then yeah, may be a collimation issue...

[75RR]

Hi KurM,
have switched eyes, looked through both tubes with the same eye, opened and closed each one and it does seem to me that the image separation is not even, the coin viewed in the left eyepiece is closer to the right edge than the coin viewed in the right eyepiece is to the left edge, but having said that, I am seriously hampered by a lack of knowledge here. Pretty sure that is not right but not sure what the separation between them and the edge aught to be.
If given good step by step instructions I should be able to both check to see if it is collimated and get a good idea if I can sort it out if it is not. If I can't, then I will try to find someone that can.

[75RR]

Haven't received a reply yet but was looking through the service manual and it would seem the laser collimator is meant to substitute for the Autocollimator that projects a Maltese Cross. Not quite sure how yet.
Image is of part of a page on Axis Parallelism:

[75RR]

Have received a reply from my advisor.
He has collimated his Wild M8 using a telescope laser collimator.
His reply is short and to the point:

"Put it on one of the eyepiece tube
And set an mirror on the prep table
Then it works fine"

So there we have it.

Question: Do all telescope laser collimators project a cross and a central dot?

[Crater Eddie]

I have never used one, but the ones I have seen only project a dot.
CE

[KurtM]

Laser collimators offered in the amateur astronomy marketplace typically put out a dot, but there are some collimators, and attachments for existing collimators, that project a reticle. As for these reticles, I've never seen a simple crosshairs; the ones I have experience with exhibit a complicated and involved crosshair plus background grid pattern.

A quick peek at eBay turned up this crosshair accessory that attaches to your laser collimator: eBay item number 122036070337 NOTE: Howie Glatter is the King of laser collimators, a great guy who has been around forever. You could probably do a lot worse than write him with collimator questions.

As I mentioned earlier, these collimators have 1.25" and 2" barrels to accommodate standard telescope focuser tubes. I wonder how that might be made to work in microscope eyepiece tubes?

The least expensive you're likely to find is from Orion at $56 + S&H: http://tinyurl.com/hqm3rb9

[75RR]

Hi KurtM, thanks for the info.

Not sure how the laser collimator would work exactly. Am having trouble visualizing it.

The stereoscope, minus the objective and the casing, is lowered on to a mirror which sits on rubber foam.
One then places the laser collimator in one of the eyetubes.
Not sure where one is supposed to see the cross/dot. Is it through the other eyepiece? I suppose it must.
The collimation itself, looking through the Service Manual is pretty much like centering a Rotary Stage.

Found this which helps a bit: www.microscopy-uk.org.uk/mag/artfeb04/pjcollim.html

[KurtM]

What makes the laser collimater so popular is that you can make collimation adjustments while watching the collimator. With optical collimating tools, it is matter of attending to either one or the other at a time; one observes the image created by the tool, then leaves it to make adjustments, then returns to the tool to see how he did, etc., etc. It invariably requires mental gymnastics, which is easier for some than others. I never had a problem with optical collimation tools myself (in telescopes), but prefer the ease and convenience of the laser (think collimating telescopes at night, for instance).

Is your Wild a CMO or Greenough type? I assume CMO?

That's Common Main Objective, aka "cyclops", for those who don't know; Greenough uses two objectives, one for each side. See:
http://www.history-of-the-microscope.or ... scopes.php

EDIT: I am having a devil of a time visualizing how it might help also. Seems like you'd need two: one for each eyepiece...?

[75RR]

It is CMO or Parallel as it is also known. Some people prefer to call it that as apparently there are Greenoughs that have a Common Main Objective as well, though their light channels are not of course parallel.

I imagine one puts the laser in one eyepiece tube and observes with the other though not sure in that case how that works as the eyepiece-tube one is observing through may be off as well.

Perhaps one has to, as in the collimation of the lenses, collimate the eyepiece-tubes. Do one then the other then go back and do them again until they slowly end up centered.

Quite liked the way it was done in the linked article.

[rnabholz]

Please don't be afraid to shoot this down as all I have collimated are telescopes, just throwing it out.

It would seem to me that a witness mark on the the stage, and a reticle eyepiece moved back and forth between the eye tubes would get you there. That assumes that you have easy access to the collimation adjustments.

Am I missing something?

[75RR]

Doesn't sound crazy to me but it does leave out the mirror which the manual indicates as does my adviser,
his name is Pär by the way, a member of the photomacrography forum.

See Service Manual image:
From this and other images it would seem that there are centering marks on the mirror, which looks as if it fits snugly on to the base. It also seems as if one can peer down the Autocollimater - which would simplify things quite a bit.
It has a cable which is for a light I think, it projects a Maltese Cross down on to the mirror.
Note that the objective is removed for the collimation process, so each light track just needs to be centered and parallel to each other.

[Crater Eddie]

The telescope laser collimators that I have seen don't have a bore down the middle to peer through. Seems like the two collimation devices are quite different.
CE

[75RR]

The telescope laser collimators that I have seen don't have a bore down the middle to peer through. Seems like the two collimation devices are quite different.
CE

Agree, that is what I find confusing - unsure how to use it.

[Crater Eddie]

Maybe we are making it too difficult.
Perhaps you just put the laser in one eyepiece, place a piece of paper on the stage then turn on the laser. Mark where the beam hits, move the laser to the other eyepiece and see how far the beam hits from the mark? That doesn't seem all that precise though.
I sure wouldn't want to look through one eyepiece while the laser is in the other and turned on. The image of the dot would be way too bright.
CE

[75RR]

I sure wouldn't want to look through one eyepiece while the laser in the other and turned on.

That is a good point!
Perhaps it is best to forget the laser and go with Paul James' method - fit concentric circles to the base and use a reticule eyepiece.

[rnabholz]

The Telescope autocollimator that I have does not involve a laser at all.

It is the last step in the collimation process and is highly accurate and will only work when the scope is very close to perfect collimation.

The device is basically a tube with a pinhole in its cap. The underside of the cap is mirrored. Inserted in the focuser tube, the condition you hope to see is a complete blackout, created when all mirrors in the system are providing a parallel alignment of the primary mirror and the autocollimator mirror. Any light seen indicates misalignment, in this case usually in the secondary, and usually a rotation error.

Any use of a laser happens much earlier in the process.

Not sure this is any help....

Rod

[75RR]

This is what I think the decollimation consists of:

I chose the right viewing tube to correct as there was a larger unfocused area on its right side
and correspondingly less on its left.
The unfocused area was evenly distributed on the borders of the left viewing tube.



Am hopeful that the fact that it is just a horizontal shift will simplify collimation,
yet I am unsure however as to which screws to turn to center it.

Need a technically minded person with a little time on their hands to go over the Service Manual and figure it out.
Yes, that was a call for volunteers. PM me if interested.

[MikeBradley]

I tried looking at a front-surfaced mirror through my microscope. Flaws in the silvering behave like stars and reveal their Airy discs going into and out of focus.
Michael

[75RR]

This is a very old post that has been bumped for no good reason. Please check dates!

[MichaelG.]

I tried looking at a front-surfaced mirror through my microscope. Flaws in the silvering behave like stars and reveal their Airy discs ...

I would like to discuss this, but don't wish to cause further irritation to 75RR, so I will send you a private message.

MichaelG.