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Binocular assistance

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7 replies to this topic

#1 DSOGabe

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Posted 06 June 2020 - 05:01 PM

I'm not too familiar with binoculars is general, so here is my issue

I have a pair of old 8x40 porro prism binocs. Bought them about 40 years ago. I'd use them occasionally. Never been dropped or mishandled but I've discovered that they now produce a double image, kind of like when you try to focus with eyes crossed. Only when I pivot them so the two sections are closest together does the image become one again, as I slowly pivot them apart to a comfortable viewing position the double vision comes back.

What happened? Is there a remedy for this?

Thanks in advance,

Gabe



#2 hallelujah

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Posted 06 June 2020 - 05:05 PM

It needs to be collimated.

 

www.suddarthoptical.com

 

Stan


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#3 cookjaiii

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Posted 06 June 2020 - 05:21 PM

They are out of collimation.

 

You might be able to adjust them to correct the double vision for one preferred inter-pupil distance (IPD).  Depending on the model, yours may have screws for adjusting the tilt of the prisms or they may have eccentric rings around the objective lenses to accomplish this adjustment.  But you need expensive specialized equipment and knowledge to achieve true collimation.  

 

If they are a very expensive pair or have sentimental value, you could send them to Suddarth Optical as Stan suggested.  Otherwise, you would probably be better off buying something new.


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#4 Yarddog

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Posted 06 June 2020 - 05:41 PM

Like you I have a pair which got out of alignment while just setting up. How can that happen?

 

These are Minolta roof prisms btw.



#5 pat in los angeles basin

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Posted 06 June 2020 - 05:48 PM

Gabe; If you mention the brand ans specs off the prism covers on the rear  of the binocular body or have pics from the front view and rear view, Many persons on the forum can estimate the "value" of sending for a fix. Either a prism has moved, an objective lens had moved or (and?) the binoculars have been dropped (unless they are celestron skymasters!!- then they "might " have done it on their  own!- sorry, couldn't help myself!).                                          Regards, Pat



#6 Mark9473

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Posted 06 June 2020 - 05:57 PM

If it's one of those old porro models where the objective tubes screw into the prism housing, check that one of those hasn't become cross-threaded.



#7 DSOGabe

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Posted 08 June 2020 - 09:46 AM

They are out of collimation.

 

You might be able to adjust them to correct the double vision for one preferred inter-pupil distance (IPD).  Depending on the model, yours may have screws for adjusting the tilt of the prisms or they may have eccentric rings around the objective lenses to accomplish this adjustment.  But you need expensive specialized equipment and knowledge to achieve true collimation.  

 

If they are a very expensive pair or have sentimental value, you could send them to Suddarth Optical as Stan suggested.  Otherwise, you would probably be better off buying something new.

 

 

Gabe; If you mention the brand ans specs off the prism covers on the rear  of the binocular body or have pics from the front view and rear view, Many persons on the forum can estimate the "value" of sending for a fix. Either a prism has moved, an objective lens had moved or (and?) the binoculars have been dropped (unless they are celestron skymasters!!- then they "might " have done it on their  own!- sorry, couldn't help myself!).                                          Regards, Pat

Thanks for the info. Probably not worth the effort and cost to send out for professional adjustments. Bought them at K-mart way back when.  There are a couple of small screws on the back sides so I'll attempt to do it myself. If I mess up, it will not be a real loss. 



#8 LU1AR

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Posted 15 June 2020 - 06:09 PM

Before touching the prisms, please rotate the lens cell. Some binoculars have a kind of eccentric mounting that allows the collimation to be modified by rotating the cell. You will need an expansion tool (Is cheap).
An easy way to do this is to support them firmly looking at a horizontal object and verifying the alignment by looking at each eyepiece from a few centimeters behind.
The eye tolerates convergence, but less divergence. What it does not tolerate at all is vertical divergence.
If it is not corrected by rotating the lens cell, you will have to work on the prisms.
There is a lot of information in these great forums.
I hope this is useful to some.
Regards.
Edgardo




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