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Conditional alignment vs. true collimation

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#1 GarrettOptical

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Posted 30 June 2006 - 07:23 PM

Thought this might be of interest to the CN Binoforum gurus - Edz or Joad, let me know if I am in violation of the TOS - I don't think I am, but I may have missed something.

Much has been written about the distinction between "conditional alignment" (we all owe Bill Cook a debt for that term) and true collimation. Recently, Cory and I were working on calibrating a new laser collimation tester, and in the process I was able to get some pics that really illustrate the dangers of conditional alignment, at least from a vendor's perspective. One of the 20x80LW's we were testing was almost perfectly ALIGNED at max IPD (72mm, in this case) - this is represented by the two dots of focused light in the left pic. The right pic represents the SAME binocular - which hadn't been worked on since it left the factory (and hadn't passed our inspection, either) - at its minimum IPD setting of 57mm. This binocular could easily have just been conditionally aligned by an individual with a 70mm IPD. Just as a reference point, what you are seeing at the minimum IPD is about 55 arcminutes of step (as later measured by Cory on the Mark V).

Of course, for the end user conditional alignment ("collimating" the binocular at just one IPD setting) will work just fine - as long as everyone else who'll be using the binoculars has a similar IPD (if you aligned them yourself), or as long as the person who conditionally aligned the binoculars has an IPD close to yours. But if your Uncle Bob has a 70mm IPD and yours is only 60mm, he may have trouble appreciating your binoculars - that is, unless they were actually collimated to start with, on a real collimator by someone like Bill C..

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#2 GarrettOptical

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Posted 30 June 2006 - 07:24 PM

Here’s another pic of the binos on the tester:

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  • 1024007-collimator300w.jpg


#3 Joad

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Posted 30 June 2006 - 09:05 PM

Zach, this looks like fascinatingly useful information for us without a trace of salesmanship! Thanks!

#4 BillC

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Posted 30 June 2006 - 10:58 PM

on a real collimator by someone like Bill C..


You meant Cory S. I am currently booked up and disinterested--at least for a time.

Please don't let Cory hurt himself with the laser; you know how excited he can get around optics. ;-)

Tell him his short fat friend says "hey."

Cheers,

Bill

#5 Littlegreenman

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Posted 01 July 2006 - 01:05 PM

Dagnabbit! Now I'm paranoid that all my binoculars aren't collimated to my IPD! Do you offer discounts if I send you 18 of them? :question:

Seriously, my equipment free method for checking collimation has been the alternate-eye-blink test; does the star move if looking from one side to the other? And the ever unpopular, "is the view relaxing or do I find myself straining or just not looking through them (as long as I do on other binocs)." The first test of course only will find more grossly misaligned binocs, and the failing the second test could be the result of a lot of problems.

At least that's my understanding. Anyone feel free to correct me on those points if I'm wrong.

#6 grbrown

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Posted 06 July 2006 - 06:33 AM

Zach,

It is also of interest of some of us mere punters! Well done.

Is there a simple way we try this out at home?

#7 OBERWERK

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Posted 07 July 2006 - 03:19 PM

Yes, as long as your IPD is not at either extreme, you can easily detect this problem visually. While checking collimation by viewing a distant object, using the techniques that have been decribed elsewhere, swing the binocular through as much of an IPD range as you can still get a glimpse of your target with both eyes. My IPD is right in the middle (about 65mm), and I can see a target through the entire IPD range with large-exit-pupil binoculars (such as an 11x70). But even a few degrees is enough to detect any change in relative position of the target. If collimation does not change at all in a few degrees of swing, then it's not going to change as the swing continues to either extreme. Unless your binocular has been dropped, or had the prisms removed at some point, then it is highly unlikely that your binocular is conditionally collimated. If there is a problem detected, it is more likely that there is a mechanical issue (body hinge/objective brace hinge misaligment) than a prism misalignment. Prisms are locked into position at the factory to ensure the binocular is truly collimated. Because if this, even if some tweaking of the collimation screws is required, rarely will this cause a conditional collimation.
Kevin Busarow
Oberwerk Corp.

Zach,

It is also of interest of some of us mere punters! Well done.

Is there a simple way we try this out at home?



#8 grbrown

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Posted 10 July 2006 - 06:27 AM

even if some tweaking of the collimation screws is required, rarely will this cause a conditional collimation.


Kevin,

Thanks, that is reassuring!

#9 GarrettOptical

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Posted 12 July 2006 - 11:43 AM

Please don't let Cory hurt himself with the laser; you know how excited he can get around optics. ;-)


Bill,

I know! Cory had the laser at his house for a while, and I hear that he and Christine were playing with it from their front porch all evening. I'm glad he's so enthusiastic, though - it's a real pleasure to work with him.

Take care,

Zach

#10 GarrettOptical

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Posted 12 July 2006 - 12:21 PM

Hi Graham,

The technique Kevin B. suggested should give you a idea, as long as your binoculars have relatively large exit pupils and as long as you have an average IPD. It is possible that the degree of error might be undetectable on the range over which you can see the target, yet over the entire interpupilary range the error might be unacceptable. Using my original post as an example, if your IPD was unusually wide at say 71mm, you might find that the binos seemed collimated from 67mm to the max of 72mm (especially if the error was less extreme than in that particular 20x80). However, the error could still be bothersome for a child with an IPD of 57mm, since you are only seeing the widest 5mm of the 15mm IPD range. This becomes more of an issue the smaller the exit pupil is. That's why it is important to ultimately have an objective way of testing and adjusting binocular collimation (such as the Mark V in the pic below). In our experience, as many as 80% of the large-aperture binos will need collimation after the Pacific rim shipping gorillas get through with them - regardless of how carefully they're packed or how well the factory mounts the prisms. Our factories do a good job with mechanical alignment, so that is rarely the source of mis-collimation - it is almost always prism shifting due to impacts, and fixing that requires a real collimator to get both barrels collimated with respect to each other and to the mechanical axel.

Now I'm paranoid that all my binoculars aren't collimated to my IPD!


If you don't detect any mis-collimation visually and there's no eye strain, then I wouldn't be worried. For an individual user, tweaking the prism screws without a collimator should work just fine. I was just trying to illustrate with my original post why we as a vendor can't do that -- because we don't know our customers' (or our customers' friends') IPD's ahead of time, we need to have a way to be sure that the binocular ships in collimation throughout the entire interpupilary range.

Best regards,

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  • 1040679-markV200w.jpg


#11 GarrettOptical

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Posted 12 July 2006 - 12:26 PM

Another pic of the Mark V, just in case anyone is wondering what it looks like with a pair of binos:

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  • 1040689-markv-2-300w.jpg


#12 BillC

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Posted 12 July 2006 - 02:31 PM

Please don't let Cory hurt himself with the laser; you know how excited he can get around optics. ;-)


Bill,

I know! Cory had the laser at his house for a while, and I hear that he and Christine were playing with it from their front porch all evening. I'm glad he's so enthusiastic, though - it's a real pleasure to work with him.

Take care,

Zach



It is a pleasure to work with him. Can you imagine his nerve at wanting to leaving me for a lousy 4 bucks and hour!? I can't imagine what it would be like to give up such a great gig for a mere 4 bucks an hour.

HOWEVER, if anyone out there wants to offer me an additional 4 bucks an hour to find out, far be it from me NOT to try the experience. After all, Cory is a forward thinking fellow; he might be onto something! :jump:

Cheers,

Bill

#13 GarrettOptical

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Posted 13 July 2006 - 04:16 PM

It is a pleasure to work with him. Can you imagine his nerve at wanting to leaving me for a lousy 4 bucks and hour!? I can't imagine what it would be like to give up such a great gig for a mere 4 bucks an hour.


Hi Bill,

Cory says that after he left your shop he was making a whopping $4.50 an hour out in California - it must have been the extra 50 cents.

Take care,
Zach

#14 grbrown

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Posted 15 July 2006 - 05:03 AM

Zach,

Many thanks for that. I think I need to go into a darkened room and do some deep thinking now.... :confused:

#15 devond

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Posted 22 August 2006 - 02:52 PM

Howdy,

I just joined the forum and wanted to chime in with both a general thank you to all of you that have maintained and contributed to this fantastic wealth of knowledge and a specific thanks to zachg for this post on conditional alignment which was well timed for my needs (though not what I wanted to hear).

I've been wrestling with the good folks at Orion to get a pair of their Explorer 25x100 binocs that doesn't suffer from any show-stopper defects. For the price I didn't expect perfection but the other gear I've purchased from Orion (8" dob and 90mm Mak) seemed quite good so I did expect something that I could at least use. Well, the first pair was delivered with completely mis-machined mounting post threads that even a cursory visual examination would have caught. The second pair had a significant cats-eye in one tube and so much flare/coma/spikes/??? in both tubes that even medium magnitude stars were almost psychedlic to view no matter how finely focused (again, could have been caught had anyone cared to check). The third pair was recieved grossly out of collimation with a large vertical seperation. Perhaps this was caused during shipping but past history leaves me rather cynical about that and I would bet money that they went out Orion's wharehouse in the same state.

After reading many of the posts here I finally conditionaly aligned them myself (rather than pay yet another $25 for shipping) with an excellent final result (or so I thought). However, thanks to ZachG's post here I now realize that while I have the bincos aligned just great for my IPD (~63mm) as I traverse towards either extreme the alignment is lost.

Now I'm on the fence about whether I should stick with what I've got as it's working great for me now or send yet another pair back in the hopes that my fourth set will yield better results. Anyone care to predict what my chances are of getting a pair of these binocs out of Orion's factory that A) doesn't suffer any obvious machining defects B) doesn't suffer from any obvious optical defects and C) doesn't suffer from any mechanical collimation issues? I'm guessing it's a low number.

So once again, thanks to all of you that make this site THE place for a google powered newbie like myself to get advice that doesn't appear to exist anywhere else online!

PS - For anyone else searching for reviews of the Orion Explorer 25x100mm binocs (aka Giantviews in the their latest print catalog) my advice to you is to run far far away from these binocs and go with a shop that actually inspects each pair rather than just pass them along to you exactly as they came off the boat. Why should you act as their QA department and go broke shipping their faulty products back to them when they MUST know that this product has QA issues?

#16 Rick

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Posted 22 August 2006 - 04:44 PM

Now I'm on the fence about whether I should stick with what I've got as it's working great for me now or send yet another pair back in the hopes that my fourth set will yield better results.


Howdy back atcha and welcome to the Binocular forum!

The definition of insanity is doing the same thing over and over and expecting different results. :lol:

clear skies,
Rick

#17 BillC

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Posted 22 August 2006 - 05:13 PM

As long as so many people go around bragging about the great purchase they've just made on a binocular that's collimated so poorly you can look around trees, the manufactures / importers have no reason to solve the problem.

Almost every specimen of a large bino that is highly touted on this list comes into my shop greatly out of collimation. In fact, I just got off the phone with the "manufacturer" about this just moments ago.

His hands are tied. For the money people are willing to spend and brag about, an acceptable level of alignment and mechanical strength is just not possible.

We can't have our cake and eat it too. Reality stinks. But, it has never been open for debate.

Cheers,

Bill

#18 devond

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Posted 22 August 2006 - 05:57 PM

Very good points Rick (quit while I'm ahead) and BillC (you don't get what you don't pay for). Now I'm worried that the 60mm scope that I ordered from ToysRUs for $50 won't give me the 600x magnification advertised!

Take care,
-Devon

#19 Kimmo Absetz

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Posted 23 August 2006 - 01:19 AM

Devpon,

Just as general advice, whenever you have a binocular which you feel works great for you, just count your blessings and don't send it back in hopes of getting an even better sample. Regarding collimation specifically, the amateur astronomers association URSA here in Finland sells some optics, and all the bigger astro binoculars they sell have their collimation re-checked by a tech prior to being sold to a customer. Obviously, they think it is worth the extra expense, and I think this says something about the way they come "right out of the shipping container."

Kimmo

#20 devond

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Posted 23 August 2006 - 12:06 PM

Kimmo,

Yes, I'm planning on keeping this latest pair as it does indeed render some fantastic views now that its tuned. However, it does frustrate me that I will have difficulty sharing these views with my wife (very small IPD) and various other big/small headed family and friends. Maybe I'll attach a permanent adjustment knob to the prism screws and treat it like another step of focusing! :smirk:

Take care,
-D


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