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Determining if a binocular is misaligned.

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#1 Joe1950

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Posted 17 January 2018 - 07:40 PM

I know there is a difference between alignment and collimation, but I'm not sure what applies here. I'm speaking of the two optical systems of the binocular not pointing in the same direction.

 

The point is that with misaligned binoculars, the eyes (actually the human brain) will compensate, to a degree to bring the two images into alignment. However, viewing in this way for extended periods of time would become uncomfortable and may strain the eyes or cause a headache.

 

So if one may have a binocular in this grey area of alignment, is there a relatively simple test to determine if it is or is not aligned properly?

 

Thanks in advance for any information.


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#2 SMark

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Posted 17 January 2018 - 07:49 PM

Focus the left side good and sharp, and then put the right side way out of focus. Then find a bright star or point of light to view. The brain won't likely even try to put the two images together like this. So what you want to see is the sharp star sitting nicely in the middle of the out-of-focus-blob. That would indicate good alignment. If the sharp image is outside of the blob, then you will need to make adjustments to get it back inside the blob. 

 

You can typically tolerate more horizontal variance than vertical variance. 


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#3 Wayne Costigan

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Posted 17 January 2018 - 08:03 PM

Focus the left side good and sharp, and then put the right side way out of focus. Then find a bright star or point of light to view. The brain won't likely even try to put the two images together like this. So what you want to see is the sharp star sitting nicely in the middle of the out-of-focus-blob. That would indicate good alignment. If the sharp image is outside of the blob, then you will need to make adjustments to get it back inside the blob. 

 

You can typically tolerate more horizontal variance than vertical variance. 

EXCELLENT! Never heard this one and will try it next starry night.

 

I can usually tell by rapidly lowering the bins I've been looking through while staring at the object and noticing whether eyes "swoon" or not. Swoon is my term for the rapid refocusing of the eyes on said object I'd been observing through the bins. In a known well aligned/collimated set, I get zero swoon effect. If even slightly off, I notice some amount of swoon. And I go back to adjusting prisms until I don't notice any. As well, I then check on stars to see if any are doubling, even slightly. If so, back to fiddling with the prisms. Final check is give the binoculars to the Mrs. and see if she sees any doubling. Her face is far narrower than mine with a far different IPD. 

 

Your method sounds so much easier! Thanks again. 


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#4 Joe1950

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Posted 17 January 2018 - 08:13 PM

Sounds good! Thanks SMark and Wayne! I will definitely give that a try.

 

 

(The reason I question the terms is that I think a while back, speaking in strict optical definitions, collimation only applies to one optical axis - but I could be totally wrong about that.)


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#5 SMark

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Posted 17 January 2018 - 08:26 PM

Sounds good! Thanks SMark and Wayne! I will definitely give that a try.

 

 

(The reason I question the terms is that I think a while back, speaking in strict optical definitions, collimation only applies to one optical axis - but I could be totally wrong about that.)

Yeah, exactly. You can do a lot of different combinations of adjustments to get that focused star in the middle of the unfocused blob. All combinations will indicate alignment, but only one combination will indicate collimation.

 

Oh, and good luck finding it... winky.gif


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#6 SMark

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Posted 17 January 2018 - 08:31 PM

Actually, let me quote the man who wrote the rules of engagement for collimation...

 

 

...There is no difference between “aligning” and “collimating a binocular.” The problem arises when people perform a “CONDITIONAL alignment” and call it “collimation”—which it is not! (covered on pages 86-124 of BINOCULARS: Fallacy & Fact)

 

I have performed a conditional alignment on my own binos but, not drinking or using drugs, I wouldn’t mislead folks by calling it “collimation.” Unless the error is very slight, the willy-nilly screw tweakers may cause more harm than good if the bino is to be used by others who have a different IPD.

 

Finally, the brain CAN compensate for misaligned optical axes—TO A SMALL DEGREE ... along the X axis, but not without introducing a degree of eyestrain. AND, “collimation” applies to both telescopes when speaking of binoculars.

 

Cheers,

 

He who must not be named (and used with his permission.)


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#7 Joe1950

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Posted 17 January 2018 - 08:35 PM

Good enough for me SMark! Thanks much!



#8 SMark

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Posted 17 January 2018 - 08:43 PM

You are very welcome!

 

Signed...

 

http://images.digopa...urmudgeon_3.jpg


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#9 brentwood

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Posted 17 January 2018 - 08:45 PM

A daytime method is to find something distant with clearly defined horizontal and vertical lines like the top of a telephone pole, cross on a church, or the top of a leafless tree. The farther away the object is the better. Look and focus at the object, now SLOWLY pull the eyepieces away from your eyes while still looking at the object. This will make it more difficult for the brain to merge the images and you will see a double image if they are out of alignment (the term I use)

Yes, a horizontal misalignment can be more forgiving, but ONLY if the eyes have to diverge, which is what they have to do when looking at close objects.

BTW I have also used  a single float or buoy out on the ocean. 


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#10 Joe1950

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Posted 17 January 2018 - 08:50 PM

Excellent Brentwood! I will give that a try also.

Thank you!



#11 Jawaid I. Abbasi

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Posted 17 January 2018 - 08:56 PM

Sounds good! Thanks SMark and Wayne! I will definitely give that a try.

 

 

(The reason I question the terms is that I think a while back, speaking in strict optical definitions, collimation only applies to one optical axis - but I could be totally wrong about that.)

All three axis alignment becomes a true alignment.

If the alignment is out within 4 minutes divergence, you will have headache and feeling dizzy.


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#12 Wayne Costigan

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Posted 17 January 2018 - 09:22 PM

I know there is a difference between alignment and collimation, but I'm not sure what applies here. I'm speaking of the two optical systems of the binocular not pointing in the same direction.

 

The point is that with misaligned binoculars, the eyes (actually the human brain) will compensate, to a degree to bring the two images into alignment. However, viewing in this way for extended periods of time would become uncomfortable and may strain the eyes or cause a headache.

 

So if one may have a binocular in this grey area of alignment, is there a relatively simple test to determine if it is or is not aligned properly?

 

Thanks in advance for any information.

Here is a way to use the sun and a home made apparatus to get universal collimation: Sun Images Method for Checking Alignment of Binoculars, by Rafael Chamon Cobos. Google this title for the 32 page article with schematics. I have yet to build and try this, but Frank Lagorio has, and he swears by it! Thanks Frank. 


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#13 Joe1950

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Posted 17 January 2018 - 10:03 PM

Wow! that is a great article to have. Thanks Wayne!!

 

My son, who has a moderate interest in astronomy, having job and family to keep him busy most of the time, got an inexpensive binocular to just do some quick scanning. Fortunately, his sky is darker than mine is even though he lives close by.

 

He said he thought something was wrong and asked me to to take a look. During the day, I could see something was amiss but I could see a merged image at times. I had a suspicion my eyes/brain were doing the aligning.

 

Ironically, when the right side was not in focus before adjusting the eyepiece to match, the alignment did seem off, as would be expected with the blur test. Only when in focus was I able to merge the images.

 

I just went out to do try the blur test on Sirius tonight, but didn't even have to. There were two distinct Sirius's a good distance apart, and though I could bring them closer, I couldn't come close to merging them. So the collimation is way off. Since they are new and just purchased we'll return them.

 

I guess looking at a bright star is more telling than an extended object with everything focused and your eyes right up to the eyepiece. But the daytime test would no doubt reveal the same condition, backing off a few inches.

 

I've heard this is a problem with many of the inexpensive import line binos.

 

Anyway, thanks all for the great info. If he decides to go with another bino, we'll know what to look for!!

 

joe


Edited by Joe1950, 17 January 2018 - 10:04 PM.

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#14 Jawaid I. Abbasi

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Posted 17 January 2018 - 11:26 PM

Joe,

You have much darker sky then mine here at Levittown, PA

If you decide to buy, I will recommend to buy the used here at cloudy night or go at Astromart. 

 

The reason to recommend a used one specially from CN classified because most binoculars if not all are spot on and the sellers also make sure that the buyer gets the correct information so it is like a bond and trust within astronomy community.

 

About your mis-align binocular, Send it back as soon as possible to avoid nightmares in your dream :)


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#15 Joe1950

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Posted 24 January 2018 - 05:12 PM

I certainly agree with you, Jawaid! Thank you.



#16 Mr. Bill

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Posted 24 January 2018 - 05:21 PM

Focus the left side good and sharp, and then put the right side way out of focus. Then find a bright star or point of light to view. The brain won't likely even try to put the two images together like this. So what you want to see is the sharp star sitting nicely in the middle of the out-of-focus-blob. That would indicate good alignment. If the sharp image is outside of the blob, then you will need to make adjustments to get it back inside the blob. 

 

You can typically tolerate more horizontal variance than vertical variance. 

This is a good technique IF you know for sure that both eyes are looking parallel....doesn't work well if you are even slightly cross eyed or wall eyed.


Edited by Mr. Bill, 24 January 2018 - 05:23 PM.

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#17 Joe1950

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Posted 24 January 2018 - 05:27 PM

It failed miserably and has been returned. Thanks Mr. Bill.




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