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double vision???

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#1 Guest_**DONOTDELETE**_*

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Posted 12 August 2005 - 03:07 PM

Hi there

i have a pair of no brand 8 x 42 binos that i have started my hobby with, i have taken everyones advice about sticking to binos for a while before i splash out on a scope.

The problem i have is when i look at the stars/ or the moon i see two of them, so i end up just using one eye. Its really annoying.

is it me , is it how it should be or is it the binos

please help

#2 Mark9473

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Posted 12 August 2005 - 03:12 PM

Well, if you don't see the Moon double without the binoculars, I don't see how it can be you.

#3 Guest_**DONOTDELETE**_*

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Posted 12 August 2005 - 03:17 PM

thanks for that Mark

#4 Rich N

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Posted 12 August 2005 - 03:41 PM

Hi kevantlin,

It is likely your binocular is the problem.

You might want find a store selling binoculars and try a few. Bring your binocular along for comparison.

Good luck,
Rich

#5 Rich N

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Posted 12 August 2005 - 03:46 PM

Hi again kevantlin,

IMHO, there is nothing wrong with getting a telescope before you "learn the sky" with binoculars.

Rich

#6 Joad

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Posted 12 August 2005 - 05:53 PM

Oh oh, here we go again. Please don't say that your binoculars were made in China--those seem to be fightin' words 'round here, pardner.

By the way, your binos are either misaligned, out of collimation, or probably both. :(

#7 BillC

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Posted 12 August 2005 - 06:14 PM

. . . By the way, your binos are either misaligned, out of collimation, or probably both. :(


Misaligned = out of collimation

And, if they were made by Carl Zeiss . . . they are still out of collimation. :bawling:

#8 Joad

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Posted 12 August 2005 - 06:55 PM

. . . By the way, your binos are either misaligned, out of collimation, or probably both. :(


Misaligned = out of collimation

And, if they were made by Carl Zeiss . . . they are still out of collimation. :bawling:


Oh, thanks for the clarification. I guess I've been confused by the separate references to misalignment and discollimation.

So I'll try again: sounds like those binos need adjustment.

#9 Jon Isaacs

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Posted 12 August 2005 - 07:53 PM

Oh, thanks for the clarification. I guess I've been confused by the separate references to misalignment and discollimation.

So I'll try again: sounds like those binos need adjustment.
----

It would seem that two sorts of miscollimation would be possible with binos. The objective lenses themselves could be miscollimated as any refractor can be miscollimated. At the low powers one uses with binos this would be difficult to notice. The second type of miscollimation would be the normal kind where the two sides are not aligned with each other.

I suspect that this is the original posters problem.

Jon

#10 BillC

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Posted 12 August 2005 - 09:51 PM

It would seem that two sorts of miscollimation would be possible with binos. The objective lenses themselves could be miscollimated as any refractor can be miscollimated. At the low powers one uses with binos this would be difficult to notice. The second type of miscollimation would be the normal kind where the two sides are not aligned with each other.

I suspect that this is the original posters problem.

Jon


Should one be shot in the head with a 38 Special or a 44 magnum, the result would be the same.

Yes, each telescope SHOULD be collimated to itself. However, it is usually NOT a factor in over-all performance to the amateur. Why? How do most people on the list talk about collimating (conditionally aligning) their binoculars? By turning screws that TILT prisms. Tilt prism? Why, if you tilt prisms, you decollimate that telescope! . . . Yep!

This is why I prefer to use eccentric ring binos. By using eccentric rings, the objectives are moved laterally, without being tilted. This way, the image is OFFSET without being SKEWED.

As previously stated, I am not a big fan of going opto-geek whenever I can avoid it, However, I thought this issue too important to let pass.

Cheers,

Bill

#11 Claudio

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Posted 13 August 2005 - 03:37 AM

<<By the way, your binos are either misaligned, out of collimation, or probably both>>

<<It would seem that two sorts of miscollimation would be possible with binos. The objective lenses themselves could be miscollimated as any refractor can be miscollimated. At the low powers one uses with binos this would be difficult to notice. The second type of miscollimation would be the normal kind where the two sides are not aligned with each other.>>

Talking on binoculars, it seems to me that the expression “its axes are aligned” is generally used to describe the STATE of a binocular, i.e. if its optical axes are parallel to the hinge. “Collimating” is generally used to mean the ACTION of getting this parallelism between optical axes and hinge.
So “in a binocular the optical axes are aligned when they have been collimated by the technician”.
Please correct me if this terminology is wrong.

About the alignment between the various optical elements of each optical axis and the alignment between each optical axis and the mechanical axis (hinge):

First let’s consider a galileian binocular.
In a well machined body, the plane of each lens of the two optical paths is orthogonal to the hinge (mechanical axis).
Thus, if objective lens and ocular lens of one barrel are aligned between themselves, their common (= shared) optical axis will be the resultant optical axis of that half binocular and at the same time it will be parallel to the hinge.
On the contrary, if the lenses of one barrel are not aligned between themselves, the resultant axis of this optical system will never be parallel to the mechanical hinge.

In a Porro binocular with lenses and prism planes orthogonal to the mechanical hinge (then with alignment obtained by shifting laterally either the objective lenses, or the prisms, or the eyepieces) everything works in the same way: when a common axis is achieved between objective group and eyepiece group, this common optical axis is parallel to the mechanical axis (hinge).
Consequently, when a technician collimates a binocular (i.e. getting both optical axes parallel to the hinge, and not a simple “conditional alignment”) objective group and eyepiece group in each barrel find the alignment between themselves automatically.
By the way, this means also that a well collimated binocular performs optically better than a binocular with conditional alignment.
In Porro binoculars with tiltable prisms (those ones with the (in)famous four grub screws just under the rubber covering) it can happen that the alignment of objective group and eyepiece group is obtained only when prisms are so tilted that, though the resultant optical axis in that barrel is aligned to the hinge, the optical path is not the same all over the field of view, and this produces some loss of image quality.
As far as I know, in Porro prism binoculars with tiltable prism clusters (i.e. prisms tilt together) this theoretical loss of quality doesn’t exist because the tilt of one prism is compensated by the contemporaneous tilt of the second prism. But about this point, I would like to know the opinion of Bill Cook, Edz, Cory Suddarth, Henry Link and of the many other experienced members I am missing here.
Please correct me also when my terminology is not correct.
Regards
Claudio


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