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20x80 problem with right tube

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#1 skywatcherjan

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Posted 19 December 2012 - 03:02 PM

I already mentionned this in another thread but there the title of the thread probably doesn't atract attention to my problem: here I go
The left tube gives a tack sharp image.
The right tube , with the diopter, doesn't , there is a problem with bright objects like the moon or jupiter. The best way to describe it is like the view through a SCT with miscollimation.
The images of both tubes are perfectly merged. When looking with both eyes, the effect disappears almost (brain correcting ?) but it stays there. when closing the left eye it pops out again. Adjusting the diopter seems to help a bit so the glare to one side of lets say jupiter is the least present with the diopter nearly at max minus.
What to do about this ? Can one collimate the right tube as if it were an APO telescope ? The objective (described as a triplet) is glued in place so better not to toutch.
Would it be possible to correct it by adjusting the prisms ?
What should I do ? Or just leave it and not destroy the whole binoculars ?
Thank you
Jan

#2 BillC

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Posted 19 December 2012 - 03:38 PM

I already mentionned this in another thread but there the title of the thread probably doesn't atract attention to my problem: here I go
The left tube gives a tack sharp image.
The right tube , with the diopter, doesn't , there is a problem with bright objects like the moon or jupiter. The best way to describe it is like the view through a SCT with miscollimation.
The images of both tubes are perfectly merged. When looking with both eyes, the effect disappears almost (brain correcting ?) but it stays there. when closing the left eye it pops out again. Adjusting the diopter seems to help a bit so the glare to one side of lets say jupiter is the least present with the diopter nearly at max minus.
What to do about this ? Can one collimate the right tube as if it were an APO telescope ? The objective (described as a triplet) is glued in place so better not to toutch.
Would it be possible to correct it by adjusting the prisms ?
What should I do ? Or just leave it and not destroy the whole binoculars ?
Thank you
Jan


Hi Jan:

Your binocular SEEMS to have a collimation problem. Since initially things appear okay, and only get worse with movement or time at the eyepiece, it would APPEAR that your spatial accommodation (working ciliary muscles around your eyes) are working hard for you.

Many people say that this or that telescope is off when they really don’t know which is the offending side; they only know things are not as they should be. In repairing and collimating thousands of binoculars, I have yet to see one that needs to be tweaked like a refractor. The side is either off so much it needs REPAIR (usually from prism shift) or is negligible to the viewer.

Adjusting the prisms will NOT get the bino clinically collimated, unless you are CERTAIN of the offending side AND the other side is parallel with the mechanical axis . . . the hinge.

HOWEVER, by tweaking those screws, you can perform Conditional Alignment which will serve you (and others who are near your same IPD) just fine.

I hope this helps. :jump:

BillC

#3 Mark9473

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Posted 19 December 2012 - 03:46 PM

Well I think before starting to twist some screws it is best to make absolutely certain what the current collimation status is.

Look at a very bright star, Capella or Wega or something like that, with the left side in focus and the right side of the binocular thrown completely out of focus but turning the diopter setting to its end. You'll see a dot superimposed on a blob. If the collimation is off, the dot will not be on the blob.

Please let us know your conclusion from this test.

#4 ronharper

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Posted 19 December 2012 - 04:09 PM

If the right telescope has internal misalignment issues, your are out of luck, because you can't address those without throwing off the binocular alignment. The glued in objective suggests a not quite top grade binocular. You are lucky that the effect is not very noticeable in normal observing, and that the binocular alignment is good. Don't feel too bad about an imperfect image of Jupiter, and do not observe one eyed. Honestly, those things are asking for trouble even with the most expensive binoculars!
Ron

#5 GlennLeDrew

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Posted 19 December 2012 - 05:07 PM

Jan,
If, as you say, the collimation is good, then the aberrated image delivered by the right side likely cannot be improved without swapping out some optical elements. Trying to tweak the prisms until the image improves can only result in miscollimation.

A friend's 22X100 from some years ago had one of its eyepieces installed (and glued!) at a tilt, which certainly harmed the image. This makes me wonder if your bino might not have a tilted lens. You could try some 'investigating' by shining a laser pointer into both the objective and eyepiece ends, for both barrels, and observing the patterns of reflected dots.

The best way to do this is to punch a small hole through the middle of something like a piece of card or paper several centimeters square. Attach it to the laser pointer's front end so that the laser passes through the hole, perpendicularly. Aim the laser into the optic as centrally and perpendicularly as possible, from a range of distances, and observe the distribution of the various reflections on the 'screen.' Strive for the most compact configuration by tilting/translating the laser, and look for any reflections which stand out from the rest of the crowd. If there is clearly one or more reflections which stray from the herd, this would suggest tilt somewhere in the train.

#6 rydberg

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Posted 19 December 2012 - 09:10 PM

Just to make sure: have you looked through the binoculars upside down? If the problem changes eye, then there is a problem with that tube. Otherwise it's your right eye (hope not..).
Marco

#7 BillC

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Posted 20 December 2012 - 12:44 AM

Jan:

I never find fault with Glenn. He’s smarter than me, younger and better looking.

However, I’d be a rich man today if I had a dollar for every time someone told me their bino was perfectly collimated, when the collimator said differently . . . by a large measure.

Based on what you have said, I still think that your Spatial Accommodation is making the bino appear collimated—initially—only to fail you after a time.

Also, I have worked on some pretty crummy binos, but have NEVER seen one with the objective GLUED IN, and would recommend that you really give that a second glance.

Cheers,

BillC

#8 skywatcherjan

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Posted 20 December 2012 - 02:42 AM

Thanks for all your responses,
As for accomodation : the problem persists with one eye closed, it is there if I look with the right eye through the right tube and also if I look with the left eye through the right tube. I will post some pictures tonight of the objective side : the lens is captured by a ring screwed into the tube of which the inside is threaded. But I fear that some contact glue was applied to fasten it...
Jan

#9 Simon S

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Posted 20 December 2012 - 03:27 AM

One last thing from me, have you tried looking through the right side with your left eye? I have bad astigmatism in my right eye and therefore cant see a focused image.
There is a possibility that the right side has a poor lens manifesting itself as astigmatism too?

#10 skywatcherjan

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Posted 20 December 2012 - 03:05 PM

This is a link to the photos of the objective:
http://sdrv.ms/TDmSl9
See the darker area on the threaded part in front of the lens: glue !
Anyway : I will check properly if the binoculars are collimated and report back
Jan






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