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Collimation question

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#1 tag1260

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Posted 27 June 2013 - 02:22 PM

I have a question on collimation. Can my binoculars be collimated for me but not for you? The reason I'm asking is when I first got these, they appeared out of collimation (two images). So I collimated them making the two into one image. They appear perfect to me. However, when I let someone else look through them, I seem to always get asked why there are two images.
Thanks

#2 KennyJ

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Posted 27 June 2013 - 02:41 PM

Hi Tag,

What you have probably done is align the two scopes just for YOUR individual I.P.D ( inter pupillary distance ).

The condition is what, around 15 years ago, the former Chief Naval Optical repairman Bill Cook coined as " Conditional Alignment ".

If you prefer to share night time binocular observing with another person, but only have this one binocular, you could always try placing an ad. for a relationship with someone with the same IPD as yourself.

If you don't already know what it is, just make sure the oculars are in prime position for your eyes, then measure the distance ( in millimetres ) between the same sided edge of each eyecup ( i.e outside right to outside right, or inside left to inside left ). This will be the same distance as the gap between the centres of each exit- pupil.

Kenny

#3 Man in a Tub

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Posted 27 June 2013 - 02:43 PM

Can my binoculars be collimated for me but not for you?


Yes.

Binocular Collimation

There are many other threads on conditional alignment in this forum. A search will find them.

#4 ronharper

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Posted 27 June 2013 - 11:55 PM

Binocentrics Kenny and Stan have a good point, but i think there could also be an eyesight component.

There is a medical term for the condition in which the eyes do not align well, dyplopia I believe. That is, in their most natural and relaxed mode, the eyes are not perfectly collimated. It seems possible that one could suffer from a weak form of this condition, but overcome it in daytime life, just as a miscollimated binocular can be tolerated better by day. But if at night the true visual condition comes acutely to the fore, as a binocular collimation problem might to the normal-sighted, the dyplopic observer will find that he likes his binocular to be mis-collimated just so, to fit his condition.

Pure speculation you understand. But all manner of subtle and curious vision effects, both spurious and repeatable, will be encountered by the ardent observer. Did I ever tell ya'll about the pink elephant?

Ron

#5 Cory Suddarth

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Posted 28 June 2013 - 02:51 PM

Regarding this topic, I have a friend in Boston that does his own binocular work including conditional alignment. Recently he has noticed things were not always as they should be, so he sent me several of his binos. Before I started any work on these, I'd set them up on the Mark V and plot his glass, point "A" being the narrowest IPD setting and point "B" being the widest IDP setting. Because the collimator is set up with X and Y axis's its easy to make a simple gragh. With the stationary barrel centered, I would slowly adjust the swing barrel until it crossed at or near the center. These points intersected right around the IPD setting of 70mm. I didn't tell him this, but rather asked what his IPD setting is. He said it was 70.

All this clinical stuff to say, Ron, you can get a glass set up for you, AND folks near your IPD. In Jay's case, he did so quite accurately. What threw him off was that if he didn't look and set the glass right on the money (at 70mm IPD) befor he looked through them, he'd notice an error. If I recall this one glass had a total swing greater than 3 degrees from point "A" to point "B", most of which was step.

Cory

#6 Cory Suddarth

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Posted 28 June 2013 - 02:54 PM

Ron, sorry, that was meant to be addressed to Tag, my mistake.

Cory

#7 Gordon Rayner

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Posted 28 June 2013 - 03:16 PM

You have made the two telescopes point in the same direction at your interpupillary distance ,while ignoring the direction in which the hinge axis is pointing .

The two telescopes and the hinge axis must point in the same direction, for satisfactory use at all IPD's.

Collimation is the word used, in one of its meanings, to describe the alignment on one line of the nodes of the components of a monocular telescope, microscope, camera, etc. Laser collimators, sight tubes, autocollimating eyepiece tubes, are used for this purpose for a monocular Newtonian, Cassegrainian, refractor, or catadioptric telescope.

Collimation can also mean to render parallel, as in a collimator, which emits parallel rays which appear to come from a point at an artificial target at an infinite distance. A distant target is a practical substitute.

To achieve, in a binocular telescope ( a "binocular"), parallelism of the lines of sight and the hinge axis , at all interpupillary distances, one or both telescopes must depart from being collimated IN AND OF ITSELF, in any realistically producible/adjustable design of practical weight.

A measure of optomechanical quality is how little one or both telescopes must depart from collimation to satisfy the criterion of parallelism of the lines of sight and the hinge axis at all interpupillary distances.

"conditionally parallel" is better terminology than "conditional alignment", because the two lines of sight are not superimposed.

Parallelization is better terminology than "collimation", to describe adjustment of binoculars ( binocular telescopes composed of two separate telescopes).

#8 ronharper

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Posted 29 June 2013 - 11:23 PM

Tag,
So, does the other person who complains about your binocular have to change the IPD to use it?
Ron

#9 tag1260

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Posted 01 July 2013 - 11:04 AM

Thanks guys. I guess I'll have to keep my binos to myself!!!
Actually it's been a couple of different people who have commented on the double image.

Thanks again.






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