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Factory collimation vs self-collimation discussion

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#26 Rich V.

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Posted 30 April 2019 - 10:43 AM

These instructions do not describe collimation. They describe conditional alignment.  

How so, Frank?  Though the iterative process of the single eccentrics would usually require turning both objective eccentrics so the optical axes of both barrels turn in arcs to meet at one collimated point, the barrels will be aligned and the axes parallel before entering the prism assys.  The rhomb turrets don't change the parallelism of the light path so won't cause conditional alignment like a tilted Porro II turret prism would if using the prism shelf tilt convention incorporated in some older designs.

 

I believe this is why the Schmidt roof/ rhomb turret design is preferred for BTs; turning the turrets in IPD doesn't change the alignment.  Once collimated, the BT remains collimated throughout the IPD range.

 

Rich


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#27 Rich V.

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Posted 30 April 2019 - 01:46 PM

I'd like to add that Frank's statement would be correct if we were referring to a standard straight-through bino with a hinge axis between the barrels, not a BT with fixed tubes which the APM instructions above are intended for. 

 

Whether eccentric objective cells or prism tilt collimation conventions are provided, merely merging images at one IPD with a hinged bino does not constitute collimation, just conditional alignment.  The rotational changes caused by moving the barrels around the hinge axis change the orientation of the images relative to each other. 

 

BTs are a very different design vs. a standard bino.

 

Rich


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#28 Neil Sanford

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Posted 01 May 2019 - 12:56 AM

Here's a comment on the APM instructions ...

 

They should start by briefly explaining how to rotate eyepieces and switch them left/right.  Also perhaps slightly press them, and anyway how tightly to screw the brass compression ring that holds them. 

 

In other words, the initial statement that APM bino collimation "is usually very stable and does not have to be corrected" does not go far enough.  It should say that your merge problem might not be in "tolerances" at the objectives, but in your eyepieces.  

 

That is well explained in other threads of this forum.  There is even one member who tells of buying the expensive APM custom spanner and laboriously following the instructions, only to learn later that his correct solution was just to fiddle with his eyepieces. 


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#29 Vondragonnoggin

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Posted 01 May 2019 - 02:06 AM

Here's a comment on the APM instructions ...

 

They should start by briefly explaining how to rotate eyepieces and switch them left/right.  Also perhaps slightly press them, and anyway how tightly to screw the brass compression ring that holds them. 

 

In other words, the initial statement that APM bino collimation "is usually very stable and does not have to be corrected" does not go far enough.  It should say that your merge problem might not be in "tolerances" at the objectives, but in your eyepieces.  

 

That is well explained in other threads of this forum.  There is even one member who tells of buying the expensive APM custom spanner and laboriously following the instructions, only to learn later that his correct solution was just to fiddle with his eyepieces. 

I don’t have the new APM’s, but have the older APM 100ED Semi-Apo 45° and a Garret Optical 70mm 90°

 

I found the trick a lot of times was to leave them kind of loose in the helical focusers and let them drop into place centered then just tighten the compression ring only tight enough to where it just touches the barrel to not allow any shift of the eyepieces. On a 90° this can be done for the observing session because there is no chance of the eyepieces coming free and dropping. On a 45° you have to let them center loose and then carefully tighten just enough to not fall out when observing towards zenith. Undercuts need to be taped up with aluminum tape or filled with the little clear rubber bands that APM used to ship out with the Semi-Apo or straight barrel eyepieces with no undercut.

 

Yes, a lot of times turning the eyepieces until they show good merging needs to be done. Nothing to do with collimation out on the BT, just out on eyepiece alignment out and an easy fix. Many threads on this technique in the forum here. So far I haven’t had a pair that was too tricky and probably won’t since I’ve been done buying eyepiece pairs for a few years now and like the collection I have. 

 

I think less critical in my older BT’s because they really only see 48x as max power. With the newer ED Apo BT’s, I think people tend to want to push magnification more so eyepiece alignment is more critical at higher powers.


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#30 decep

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Posted 01 May 2019 - 09:42 AM

I guess I should restart this thread as "Factory conditional alignment vs self-conditional alignment discussion" smile.gif

 

The discussion has devolved to the issues of collimating vs aligning a $2,000 pair of binoculars.

 

Realistically, it is probably not even possible to truly collimate a $100 pair of 20x80 binoculars and I am confident that one should not expect to be able to collimate them--across the full IPD range.

 

Conditionally aligning my Zhumell 20x80 took about an hour, end to end.  I am just surprised experienced binocular users are not willing (or expect) to invest one hour into even attempting to conditionally align a low-end pair of binoculars.



#31 SMark

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Posted 01 May 2019 - 10:54 AM

Realistically, it is probably not even possible to truly collimate a $100 pair of 20x80 binoculars and I am confident that one should not expect to be able to collimate them--across the full IPD range.

 

Conditionally aligning my Zhumell 20x80 took about an hour, end to end.  I am just surprised experienced binocular users are not willing (or expect) to invest one hour into even attempting to conditionally align a low-end pair of binoculars.

Sure it's possible. And you may end up with a binocular that is better than new in the process. Here are more details for you, as well as others who have posted to this thread...

Attached Files


Edited by SMark, 01 May 2019 - 10:57 AM.

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#32 Vondragonnoggin

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Posted 01 May 2019 - 11:01 AM

Sure it's possible. And you may end up with a binocular that is better than new in the process. Here are more details for you, as well as others who have posted to this thread...

I miss that guy around here. That was an excellent read. 

 

grin.gif


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#33 Jon Isaacs

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Posted 01 May 2019 - 12:11 PM

Conditionally aligning my Zhumell 20x80 took about an hour, end to end.  I am just surprised experienced binocular users are not willing (or expect) to invest one hour into even attempting to conditionally align a low-end pair of binoculars.

 

 

There are plenty of experienced bino folks who are happy to conditionally align a low end pair of binoculars.  I think both Glenn LeDrew (who builds his own binoculars and collimators) and Tony Flanders who was with Sky and Telescope for a number of years own the 15x70 Skymasters.  

 

Myself, I bought a pair of Barska 15x70s, essentially the same binocular as the Skymasters, they were badly out of collimation and I returned them for a refund.  

 

For me, the issue is not the time spent collimating them, it's the fact that I cannot trust them to remain in collimation.  My binoculars travel a lot, they go all over the southwest. Most often it's a just 70 mile drive to the high desert in the back of a pickup but sometimes it thousands of miles.  I want binoculars that I can decide to use at 2:30 am and know that they will be collimated and ready to go.

 

I am at a time in my life when I can afford to have decent equipment.  I also think that as one becomes more experienced, one becomes less tolerant of flaws.  Focusers that shift under pressure, flimsy eyepiece bridges that rock, the aforementioned collimation issue, operating at less than full aperture, often  eye relief and off-axis sharpness are issues, poor coatings.

 

I am not promoting "alpha" binoculars but something along the lines of the Orion 15x70 Resolux's are plenty for me.  Rugged, decent optics, they deliver.

 

I generally buy used and I generally buy good quality.  I have purchased my share of entry level binoculars, I have learned some lessons.  I have mid range binoculars I bought used more than 15 years ago, they're essentially as good as new.  

 

Jon


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#34 ButterFly

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Posted 10 May 2019 - 02:28 PM


For me, the issue is not the time spent collimating them, it's the fact that I cannot trust them to remain in collimation.  My binoculars travel a lot, they go all over the southwest. Most often it's a just 70 mile drive to the high desert in the back of a pickup but sometimes it thousands of miles.  I want binoculars that I can decide to use at 2:30 am and know that they will be collimated and ready to go.

 

... 

 

Jon

Completely agree. 

 

Testing out the skymasters at B&H, one can truly see the difference in well built being able to hold collimation.  Those things don't see temperature changes and wouldn't still be on the floor if they were dropped, but they do get moved around a lot.  If simply moving those around will knock them out of alignment, you really need to learn how to realign and do so often.

 

But on the flip-side, even with higher end binos, you will have to re-align eventually.  Unless you drop then or severly shock them thermally, it is much more likely that the prism screws will shift rather than the objective cells.  If they were collimated to start with, realigning the prisms will probably bring them back into true collimation.  Things just shift as they cool down and warm up again over time even when they are very well built.  If one of those prism screws shifts more than the others, it will knock them out of alignment over time.  Swinging the hinge and checking collimation is always a good idea afterward.



#35 Rich V.

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Posted 10 May 2019 - 03:12 PM

But on the flip-side, even with higher end binos, you will have to re-align eventually.  Unless you drop then or severly shock them thermally, it is much more likely that the prism screws will shift rather than the objective cells.  If they were collimated to start with, realigning the prisms will probably bring them back into true collimation.  Things just shift as they cool down and warm up again over time even when they are very well built.  If one of those prism screws shifts more than the others, it will knock them out of alignment over time.  Swinging the hinge and checking collimation is always a good idea afterward.

Still, the higher end binos use a prism tilt convention that doesn't rely on tiny grub screws pushing against the prisms themselves.  The BA8/ MS/ MS-ED, as an example, have the prisms rigidly mounted on a shelf that is tilted with large, well located screws with springs under the shelf to make them more shockproof.

 

Photos courtesy of Cory S, taken while he had my 16x70 EDs opened up to take a look inside.  He corrected the the odd factory alignment I complained about in my 16x70 bino comparison.

 

Rich

Attached Thumbnails

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Edited by Rich V., 10 May 2019 - 06:19 PM.

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#36 Jon Isaacs

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Posted 10 May 2019 - 03:32 PM

Rich: 

 

Thanks for those photos.. Looks nice and solid.. Makes me feel good about my Resolux's.. I have both the 10.5s and the 15s..

 

Jon


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#37 Miranda2525

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Posted 10 May 2019 - 04:27 PM

I recently picked up a used pair of Zhumell 20x80 giant binoculars.  I own multiple telescopes, but this was my first pair of "astronomy" binoculars.  Before buying, I performed a little due diligence research to get a feel for the general consensus of how they perform and what to expect.  Of particular interest was "collimation" which I fully expected to have to perform.

 

I found many posts where people had purchased and returned low priced binoculars--sometimes 3-4 times--with the only reason being the binoculars were not factory collimated.

 

Coming from the world of telescopes, this attitude seems very bizarre to me.  I understand [telescope] refractors do not usually require collimation, but all reflectors, no matter if you spend $100 or $20,000, require self-collimation.  Collimation comes with the territory.

 

I suppose I could understand if you spent $1,000+ on a pair of binoculars and expect them to be reasonably collimated out of the box, but not at the sub $200 price point.

 

Am I missing something?

Binoculars are all collimated at the factory. Problem is, with cheap ones, is that the prisms get dislodged from the prism shelves during shipping.


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#38 Miranda2525

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Posted 10 May 2019 - 04:28 PM

Rich: 

 

Thanks for those photos.. Looks nice and solid.. Makes me feel good about my Resolux's.. I have both the 10.5s and the 15s..

 

Jon

Nice binoculars!!!



#39 Gordon Rayner

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Posted 10 May 2019 - 06:32 PM

In Re   #16, above:

 

"Big  military  binoculars  precisely machine from bronze castings...."

 

Very rarely.   The weight penalty   would be   prohibitive.    Nearly   all   have or had   aluminum  bodies.   



#40 shredder1656

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Posted 11 May 2019 - 05:13 AM

Sure it's possible. And you may end up with a binocular that is better than new in the process. Here are more details for you, as well as others who have posted to this thread...

 

 

I miss that guy around here. That was an excellent read. 

 

grin.gif

 

As always!!!  




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