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Solution of the miscollimation problem?

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#1 Swedpat

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Posted 09 August 2005 - 05:29 AM

One thing I constantly hear complaints about is the problem with miscollimation. And that is about binoculars of all sizes. I just wonder: How is it possible to collimate binoculars who don't have screws for this purpose? Put them in a vise and collimate them by force? Or is it just to throw them away? The problem seems to be so common that I will be positively surprised if I receive binoculars who are collimated.

One problem is also that the most dealers of binoculars have cameras as their main product and binoculars as a complement, and therefore don't know very much about binoculars. If I order binoculars by mail order and ask them to check the collimation before sending, they in the most cases don't know what I'm talking about.

Miscollimation isn't a problem for me however, because I have squinting eyes and can't experience stereoscopic viewing. I don't even notice if binoculars are collimated or not. The problem can come up if I want to sold them later.

That makes me to wonder: In the thread "Attention Oberwerk 25x100IF owners/users....?" it talks about the collimation of the Oberwerk 25x100. Those binos have individual focusing. That means it would be easy to saw apart the individual barrels and get two 25x100 spottingscopes? This measure would be a simple way to eliminate the problem with miscolliation and you could also sell the other piece to a friend! A cheap way for two persons to get each very low price 25x100 spottingscope!

Patric

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Posted 09 August 2005 - 07:25 AM

I am guessing that respectable and serious binoculars will have screws, or some other non-destrcutive method, for prism adjustments. Buyer beware if you purchase bins without this ability. Everyone, of course, would like to receive bins collimated. But, in case they are not, it's good to have prism screws to adjust.

Sawing in half 25x100 bins. Hmmm. That's a new one.

#3 Guest_**DONOTDELETE**_*

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Posted 09 August 2005 - 09:02 AM

My understanding is that there are two different ways to design binoculars for collimation adjustment.....either via prism adjustment or eccentric objective cell adjustment. Is this an "either" or a "both" proposition where collimation is concerned ? Do they all require adjustment at both ends, or is that determined by the design ? Maybe Bill could explain this a little better.

#4 Guest_**DONOTDELETE**_*

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Posted 09 August 2005 - 11:24 AM

While it is true that the objectives can be players in determining the total amount of miscollimation, very often the objectives are "frozen" in place because of the bin construction. The prisms, however, can be adjusted to achieve conditional alignment.

Eccentric rings are tools used to collimate some binoculars, which I know little about.

#5 EdZ

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Posted 09 August 2005 - 11:39 AM

Binoculars designed with eccentric rings to collimate by ajusting the objective lenses would have rigidly fixed prisms that would remain squared.

More common today is binoculars that have objective lenses cemented in place, but are constructed to allow for tilting of the prisms.

It's either/or, not both.

Not included above, some models of binoculars have the prisms fixed to the prism shelf, but have internal adjustment screws that allow tilting the entire prism shelf.

edz

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Posted 09 August 2005 - 02:00 PM

More common today is binoculars that have objective lenses cemented in place, but are constructed to allow for tilting of the prisms.

Do we know why that is so? Is it because that, generally speaking, your typical end user can make alignment adjustments more easily with tilting prisms or prism shelves than with adjustable objectives?

#7 Swedpat

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Posted 09 August 2005 - 02:09 PM

The way to collimate Oberwerk can result in the exit pupil of the right ocular get an oval shape. That is the case with my 11x70. Doesn't that mean a slightly light loss in the right ocular?

Patric

#8 EdZ

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Posted 09 August 2005 - 02:22 PM

It's not just Oberwerk, it's most average binoculars on the market today. You can end up with an oval exit pupil in either the right or left eyepiece, depending on how much you have tilted the prisms on that side of the binocular. The more you tilt the prism off axis, the worse will be the oval appearance. Yes, it obviously causes a light loss in that side. This is not a good thing. See the links in the "Best Of" section on collimation that refer to Cat's Eye Exit Pipils.

an excerpt from that article
How Much Light Is Lost?
For a binocular with a perfect round 5mm exit pupil, if the image is cutoff to represent a normally 5mm high but now only 4mm wide pointed ellipse, instead of a perfect 5mm circle, a mathematical computation will show the resultant area of the image has been reduced by approximately 30%. That’s the equivalent of taking one side of a 80mm binocular and masking the objective lens down to 66mm, or for 70mm binoculars, reducing the objective to 58mm. Remember we are dealing with the area of circles here. A 4mm circle, only 20% smaller in diameter than a 5mm circle, has only 64% of the area.


edz

#9 BillC

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Posted 09 August 2005 - 02:45 PM

My understanding is that there are two different ways to design binoculars for collimation adjustment.....either via prism adjustment or eccentric objective cell adjustment. Is this an "either" or a "both" proposition where collimation is concerned ? Do they all require adjustment at both ends, or is that determined by the design ? Maybe Bill could explain this a little better.


Eccentric is pretty well defined. However, there are a number of different conventions for the through-body collimation.

Many of the 80mm+ binos allow for adjustments via screws under the backplates AND a 3-way screw system at the objectives.

Years ago, I addressed a way to negate the collimation problem in big binos. I suggested it to Meade, Celestron and Orion. All three shot me down. These folks just don't want to make waves with the manufacturers.

Besides, they see it as a non-problem. For every Opto-geek on these lists, there are thousands of clueless consumers who will buy a bino that is out of spec by a factor of 3 and be perfectly happy with it.

Cheers,

Bill

#10 EdZ

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Posted 09 August 2005 - 03:13 PM

Besides, they see it as a non-problem. For every Opto-geek on these lists, there are thousands of clueless consumers who will buy a bino that is out of spec by a factor of 3 and be perfectly happy with it.



In support of that contention;

this binocular forum only gets 2% of all the traffic here on CN. So only 2% of the avid (and not so avid) optics geeks here at Cloudy Nights even get to read all this stuff about binoculars. It's probably fair to assume half of those might not understand it all. That means 1% of the geeks are informed. That might represent less than 1/10th of 1% of all binocular consumers.

edz

#11 KennyJ

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Posted 09 August 2005 - 04:17 PM

< That might represent less than 1/10th of 1% of all binocular consumers. >

Which makes a "guestimation" I made not long ago about binocular purchasers seem quite conservative :-)

From memory , my " guestimate " was not particularly well received amongst certain fellow members !

Kenny

#12 BillC

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Posted 09 August 2005 - 04:34 PM

Besides, who wants to go to a list full of opto-geeks? Heck, we wouldn't be hanging out here if any normal people would speak to us . . . would we? :bawling:

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Posted 09 August 2005 - 07:50 PM

That means 1% of the geeks are informed.

Here's to the one percenters! :waytogo:

Heck, we wouldn't be hanging out here if any normal people would speak to us . . . would we?

Hey! I have normal friends...real ones too!

#14 Swedpat

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Posted 10 August 2005 - 05:54 PM

I have invented the final solution of the collimation problem: Take a short refraktor, or a cassegrainscope. Put handles on each side of it. Install a binoviewer and place oculars. Ready!

Easy to change magnification, and if you want to make the most use of it you can have different oculars on each eyes on the same time! With the left eye you can get a wide overview and with the right eye you can study the details... :silly:

Patric

#15 BillC

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Posted 10 August 2005 - 06:49 PM

Hey! I have normal friends...real ones too!


Show off!

Bill

#16 gatorengineer

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Posted 10 August 2005 - 09:03 PM



Actually it is both prism tilt, and eccentric ring adjustment. However most adjustments can be accomodated with eccentric ring adjustment. This is explained, in the venerable TM9-1580 "Binoculars, Field Glasses, and BC Telescopes, all types". Which is pretty much the bible for all the military trained opticians. I gotta believe even Oberwerks have eccentric rings. Any bino that doesnt, needs to be looked as a disposable.

#17 BillC

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Posted 10 August 2005 - 10:19 PM

Any bino that doesnt, needs to be looked as a disposable.


Ya know, Any time I make a bold statement like that, I get whacked within minutes.

Therefore, I will kindly disagree with you. The Swift Seahawk and cousins, the Fujinon AR and the Bushnell Navigator, have a really good, spring loaded push/pull arrangement that doesn't even require the removal of the backplates, only the rubber backplate covers!

Cheers,

Bill

#18 ChrisR

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Posted 11 August 2005 - 12:07 AM

Bill what is your opinion of the springs on the Fujinon WP©'s both the XL and the CF have the push/pull arrangement. Also the AR and the Seahawk if memory serves me require you to remove the back plate armor and then two or three rubber plugs to get to the screws for collimation.

#19 gatorengineer

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Posted 11 August 2005 - 06:16 AM

I dont see how adjustments at the prisms, is really collimating? To me it seems like its a work around for something thats broke (objectives not in collimation), and the binocular wont really be right (some light loss) if this is all thats done. What am I missing?


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