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Collimation procedure question

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#1 nashvillebill

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Posted 23 April 2018 - 08:41 AM

I am thinking about trying the collimating procedure written by Rafael Cobos using an indoor light source.  I can make a wooden fixture to hold the binoculars suitably so it's worth a try on some of the low-cost bins I have picked up.

 

However, the 10x bins have a long minimum focus distance.  I can get about 40 feet or so inside, but the bins can't quite focus at that short a distance.

 

Will that matter? 



#2 Rich V.

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Posted 23 April 2018 - 10:37 AM

I hope I'm understanding correctly.  If you're using an indoor light source, at any reasonable indoor distance there will be parallax that will not provide parallel light paths through the binocular like the Sun would provide.  The  process needs a source of collimated light entering each side of the bino.  This is why sunlight was chosen as the source.

 

The same parallax effect would be seen if you were merely visually aligning your binos on a target too close rather than on stars at infinity.  If the target source is too close, the optical axes will be set so that they converge as they approach the target.  This will only provide alignment at the distance used in the alignment process, not at infinity as you would be desired for astronomy.

 

Rich


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#3 Ant1

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Posted 23 April 2018 - 12:03 PM

Hi

 

Unlike most collimation techniques, the clever method described by Rafael Cobos takes advantage from the fact that the incoming light beam is not collimated. Therefore there is parallax, it's all right.

To answer the OP's question, it is not necessary to have binoculars focused on the light source to achieve correct collimation using this procedure. Don't worry and take your time, the result will be good

 

Regards,

Ant1



#4 PEterW

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Posted 23 April 2018 - 12:21 PM

Can we have a link so we can learn another method please...

Peter

#5 Rich V.

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Posted 23 April 2018 - 12:27 PM

Rafael states in his abstract:

 

"The method uses the sun as source of collimated light and a simple projection screen as checking device. The binocular under test  is oriented to the sun so that two sun images are projected on the screen and focused with the focusing mechanism of the binocular."

 

Link:

 

https://sites.google...n-of-binoculars

 

How could this projection method possibly work if the light source is not collimated?

 

 

Rich



#6 cookjaiii

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Posted 23 April 2018 - 12:57 PM

Here is another method described by the same author.

 

https://sites.google...n-of-binoculars

 

"The method uses a small, bright lamp, a simple support for binoculars and a screen. These components are so positioned that the binoculars project on the screen two images of the lamp. "



#7 nashvillebill

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Posted 23 April 2018 - 01:37 PM

Here is another method described by the same author.

 

https://sites.google...n-of-binoculars

 

"The method uses a small, bright lamp, a simple support for binoculars and a screen. These components are so positioned that the binoculars project on the screen two images of the lamp. "

Yes, this is the method.  It's pinned to the top of this forum underneath the "Links of Interest" thread (second post) by the way.


Edited by nashvillebill, 23 April 2018 - 01:38 PM.


#8 Rich V.

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Posted 23 April 2018 - 01:51 PM

Whew, that makes more sense now.  smile.gif  Raphael's indoor method using a parallax calculation slipped my mind.  We had a long discussion of Raphael's Sun technique many years ago now; he's been a prolific contributor to the bino community and his graphics can't be beat.

 

Delving into alignment Raphael's way makes for a fun project and through iterations you can get a truly collimated binocular as a result.

 

FWIW, though, if all you need is simple conditional alignment of and old binocular to make it useful again, the simple old "eyeballs on a distant target" method will usually suffice.

 

Rich



#9 nashvillebill

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Posted 23 April 2018 - 02:00 PM

I have done the "collimating by eyeball" and though it was usable, I still got eyestrain and headaches...

 

Besides, I'm an engineer! I can't let an opportunity to obsess on something pass by!


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#10 SMark

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Posted 24 April 2018 - 11:23 AM

Nashvillebill,

 

As an engineer you would probably really appreciate Bill Cook’s book, "BINOCULARS: Fallacy & Fact." He dedicates almost 40 pages to collimation. Bill was a Chief Opticalman for the navy, and that along with his further work as a civilian optical tech has allowed him to say 100% of the Internet posts he has seen involve only what he calls "conditional alignment," and having repaired probably thousands of binoculars he certainly knows what he is talking about. The book is easily found on Amazon.com and there’s a CN thread, recently brought back to the top, that will illustrate what many forum members think of it. While exchanging emails with him, I discovered that he has relatives just a few miles from me, so we plan on “doing lunch” one day this summer.


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#11 Grimnir

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Posted 24 April 2018 - 11:28 AM

While exchanging emails with him, I discovered that he has relatives just a few miles from me, so we plan on “doing lunch” one day this summer.

 

 

Please give him my best when you see him!

 

Graham


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#12 nashvillebill

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Posted 24 April 2018 - 01:37 PM

I now have Bill Cook's book on the way, along with two others: Choosing, Using, and Repairing Binoculars, and Porro Prism Binoculars Overhaul.  

 

I will write up reviews of these three after I have a chance to digest them.  I am also going to try printing out a couple of Bahtinov masks to try that as well, but I will need more toner for my laser printer as well as transparency paper.

 

Thanks everyone!


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#13 Gordon Rayner

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Posted 25 April 2018 - 01:11 AM

    Deja vu:

   Why not  get the Dover reprint of   Navy  OM 3& 2  and  Hanna in ATM  II or ATM III  ?   One can use  a distant outdoor target.  No need for  in indoor target parallel light source collimator.   The main component  to devise/find  is a two angular axis  fixture,  robust and repeatable.   Peek-around  rhomboidal   comparators  can be  self-made, or purchased from   Suddarth Optical.   

 

If one can find a JTII  "hand collimator" comparator,   or build an equivalent,   that is usef,ul in the "peek-around  "  mode, with or without an attached  auxiliary  scope.    A 5 x 20  golf scope   is useful, though 3X   or so   is more comfortable  if handheld. 

 

This topic   has been   discussed    many times  here, including by your servant.



#14 nashvillebill

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Posted 25 April 2018 - 09:51 AM

I did indeed search this forum for quite some time looking for posts on collimating but did not see much to support "this topic has been discussed many times" .....perhaps I used the wrong search terms, or overlooked them, or perhaps the discussions were farther back in time than the search engine queries.

 

If I were planning to repair and collimate  binoculars professionally, certainly procuring or fabricating more elaborate test equipment would be advisable.  It's hard to justify spending a significant amount of money, however, to service a handful of thrift store/Craigslist binoculars that cost less than $20 each (typically less than $10 each).  My goal is to align my binoculars to a level above the "let's turn some screws until the image looks better" technique.  The end result may not necessarily be as perfect as the Zeiss factory might achieve (or as efficient) but it doesn't need to be.  

 

Novel do-it-yourself approaches can provide a valuable service to enthusiasts and to me there's a level of satisfaction in knowing that I accomplished something (or tried to) using non-conventional methods.


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#15 Foss

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Posted 25 April 2018 - 11:16 AM

 

Besides, I'm an engineer! I can't let an opportunity to obsess on something pass by!

Thanks for the laugh, I needed it!


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#16 Rich V.

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Posted 25 April 2018 - 11:51 AM

Novel do-it-yourself approaches can provide a valuable service to enthusiasts and to me there's a level of satisfaction in knowing that I accomplished something (or tried to) using non-conventional methods.

 

I agree with your sentiments, Bill.  I think that Raphael has provided a true service to the binocular community in the graphic way he has explained the concept of true collimation.  He clearly shows how the parallel relationship between the optical axes of a bino and the hinge axis must relate to each other.  He has provided methods of achieving collimation without the use of a professional optical shop's equipment.  If you can do this yourself on a $10 or $20 Craigslist or thrift store bino, why not try?

 

More often than not, what comes up as reference to binocular collimation on the web is merely "turn some screws until the images merge" which may be sufficient for one IPD setting and achieving a state of "conditional alignment" as coined by Bill Cook.  "Aligned" or "merged" images perhaps, but also potentially optically compromised.  To start, how do you know which tube is out of parallelism with the hinge in the first place?  How do you know you aren't moving the "good" side out of its internal alignment to match the "bad" side and are actually making things worse?  shrug.gif

 

Case in point; I received a relatively expensive new binocular from Germany last fall and while the images merged just fine to my eyes at my IPD, I could see that the circular FOVs of each barrel were not coincident.  The FOVs were divergent; the left barrel showed a FOV that appeared left of the right side's FOV.  Points inside the FOVs were merged but the edges at the field stops didn't match up.  I was told by the vendor that the factory intentionally aligned it this way and I could "turn the prism tilt screws" and correct them to my tastes myself.  I played with the prism shelves and got the FOVs to match much better but I could see that they were only conditionally aligned and went way out at narrower IPDs.  I wanted a truly collimated new binocular that my wife and I could both use, not a "conditionally aligned" new bino, though.  I really like the FOVs of my binos to overlap perfectly.  Picky?  I don't think so.

 

I thought about trying Raphael's "Sun method" of checking alignment but these were brand new binos and I wanted them to be "perfect"; I didn't want keep fiddling with the binos myself but instead sent them to Cory Suddarth's shop in Oklahoma. He opened them up to inspect, sent me photos of the insides, aligned the binos on his Mark 5 collimator and sent back a beautifully collimated bino with perfectly matching FOVs.  He included graphs of the bino's alignment before and after.  It would have been nice if the bino came this way from the factory but that wasn't the case.  IMO, sending them to Cory was a better option than sending them back to Germany and taking my chances with another specimen. 

 

In the end it was Cory's expertise that made my new binocular investment right. This is why many of us here rely on him to make our binos as good as they possibly can be. There's no reason not to try aligning binos yourself, though, particularly if you haven't made much of an investment and want to learn the ins and outs...

 

Rich


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#17 Cory Suddarth

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Posted 26 April 2018 - 02:06 PM

Rich, Bill & all,

 

For the sake of curiosity, would someone doing this type of collimation method be willing to send their finished works here to the shop for analysis? Just pay to ship here, I'll document findings (with permission), and I'll pay for return shipping and lets see where it goes? For the sake of shipping, please use a hand-held size glass. 

 

Cory


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#18 daniel_h

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Posted 26 April 2018 - 09:05 PM

 Peek-around  rhomboidal   comparators  can be  self-made, or purchased from   Suddarth Optical.   

 

Cory u got these for sale?



#19 nashvillebill

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Posted 27 April 2018 - 09:10 AM

Rich, Bill & all,

 

For the sake of curiosity, would someone doing this type of collimation method be willing to send their finished works here to the shop for analysis? Just pay to ship here, I'll document findings (with permission), and I'll pay for return shipping and lets see where it goes? For the sake of shipping, please use a hand-held size glass. 

 

Cory

I would be quite happy to attempt both Rafael's indoor procedure and the Bahtinov mask procedure and send the binoculars to you for analysis!  The results, whether good or bad, could be quite interesting.  I must fabricate a fixture to hold the binoculars suitably (to accommodate those units without tripod mounting provisions) so it may be a week or so...

 

Funny, you would think that being semi-retired would give me all the time in the world to work on projects.  Somehow it's not quite that way....


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#20 hamishbarker

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Posted 11 May 2019 - 10:07 PM

I collimated my skymaster 20x80 (or is it 75? It's raining so I'm not going to the shed to check) binos yesterday using the sunlight method.

 

As  bonus, there was a nice big sunspot and a fainter one also visible on the sun images, so I was able to show the spots to my son and his friend.

 

I only did conditional alignment this time plus a bit of exploration of the collimation at min-max IPD, as I didn't have much time to spare.

 

To make it easier to follow the sun, I had mounted a ball head on the side of my dobsonian telescope while it sat on its equatorial tracking table, and taped a piece of cardboard to stick out to the side of the rear of the telescope. The pre-ruled test sheet (two vertical lines at my IPD 65mm, and a single horizontal line) was fixed to the cardboard with clothes pegs. Distance from the eyepieces to the screen was about 500mm.

 

The skymasters don't seem to have eccentrics, so I was only using the prism adjustments. I found it much easier to understand what (conditional) misalignment  my binos had with this method. Close to the eyepieces, the solar images projected onto the screen were at IPD (since the binos were adjusted to this, so they must be), while at 500mm distance, the images were about 15-20mm further apart. So the optical axes were pointed inwards, meaning for me to merge views I would have to accommodate outwards, which is not comfortable.

 

Adjusting the screws, I could watch the movement of the images on the screen very easily and objectively. I couldn't get them quite to the correct alignment even with the screws bottomed out. So it seemed that I would have to investigate the objective end of the binos.

 

Unscrewing the "beauty cap" and then a spacer barrel which holds the objective end bracket to the hinge, I could see that the fit between the bracket and the barrel around the objective is a sloppy fit. I cut a couple of thin plastic shims and slipped them into the inner sides of the gaps, pushing the optical axes apart.  With this modification, I then had sufficient range in the prism screws to be able to adjust to conditional alignment without bottoming out the screws.

 

I adjusted to make the bottom and left sides of both images touch the horizontal and vertical lines of my screen respectively, then tried them out. The alignment was much better, merging no longer required effort.

 

Next step will be to also check at min/max IPD and see if I still have alignment at those extents. If not, I'll be going over the diagrams from Raphael again to check what the likely misalignment is.

 

Testing and adjusting the conditional alignment this was was really easy.



#21 MartinPond

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Posted 12 May 2019 - 07:31 AM

I like strapping a pair on (bungee to a plank on a tripod,

   1/4"-20 T-nut)

and looking at a target 300ft + away,

but:   focusing and backing the eyes 3in away from the 

EPs to see if the images stay in alignment.

 

The distance multiplies any error at center field and reduces the 

apparent field.

 

Any alignment that passes muster this way looks perfect when

your eyes are  right on the instrument.

 

Are both barrels skewed from the 3-axis (the hinge)  to some terrible degree?

Then you will see edge-of-field degradations.  

...

 

 

Folks are still working on scratching together one of

 those 'easy' home collimators on an adjacent thread.

No done-work pictures yet.

I have faith though: should be done before the

remodeling of Notre Dame.


Edited by MartinPond, 12 May 2019 - 07:42 AM.



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