Has anyone recommending dismantling binoculars ever done it? They are extremely difficult to collimate especially to more than one person. Its bad enough doing one set of lens let alone two on the same axis.
Has anyone recommending dismantling binoculars ever done it? They are extremely difficult to collimate especially to more than one person. Its bad enough doing one set of lens let alone two on the same axis.
We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "Spamlet" saying something like:
You can seperate balsam-glued lenses and reglue them back with fresh balsam. You can make a jig to hold them in registration, with a due degree of care and attention to detail. Whatever you do, don't try this on a valuable lens as a first attempt; indeed, pick up a scrap lens for practice. You could also use modern glue, but it's very much a fit and never take apart exercise. Balsam has the saving grace (age though it might) of being re-doable.
Thanks to all for more background,
I used to do refractive index measurement as part of mineral identification in studying geology. The trick was to find a liquid that had the same RI as the mineral and would therefore make it's outline 'disappear'. Some, or most, minerals being birefringent or more, it was always a bit of a hit and miss affair with much depending on the mineral/crystal's alignment. However, coming to the point, I thought balsam was chosen for it's RI being close to that of the glasses used in the lens, so that it did not interfere with the optical properties very much. (My lens developing it's gold corona as the balsam deteriorates, demonstrating the point.) The lens in question is part of one optic and its alignment should not be that critical so long as I can get the right thickness/RI and 'bubblefreeness' of the cementing medium.
I don't know whether this is a 'good' pair of binoculars or not, but they are old and well worn: not as powerful and compact as modern 'in line' types, but much easier to bring on target quickly. As with all such items, someone will drop them sooner or later - Dennis - so it is as well to learn how to clean and realign the barrels at least. These particular ones were tending to rise to one side on the finger screw so did need to be disassembled to clean and grease to get them all rising smoothly. In this old type, the alignment of the optics was done by eccentric rings held in place by a lot of a thick waxy substance. Once one realised the purpose of the offset rings it was just a case of 'tweak and peek' to gradually get both sides aligned with a point at infinity: a distant branch or chimney pot will do. Fiddly, but quite doable.
Once I'd done this on the old pair I had a go at a newer pair which had been well dropped and were several degrees out of alignment. These had long been given up for dead, but I found this type actually had centring screws, and were surprisingly easy to gradually tweak back into alignment. I was very pleased with the result as they turned out to be brighter and sharper than my general purpose - in the pocket all the time, modern inline prism pair.
As a schoolkid, I recall, the main interest kids had in binoculars was in taking them apart to play with the prisms, so I suppose, anyone in my cohort of kids, would not be put off by trying these things for ourselves. Obviously, if it is high definition astronomy you are into, then the fancy equipment comes in to play, but for general purposes one can normally find a compromise - like that distant chimney, in place of an optical bench, for example. (Actually, my school physics recalls such contraptions as being a pain in the neck to use. Though I did very much like the 'universal stage' I got to use later in my mineral crystal tests.)
Fiddliest binocular (and digital camera) stripdown/clean, came after I stepped onto what turned out to be a deep layer of fine silt in a stream bed. This was so fine that it got into my camera and even inside the supposedly waterproof rubber coated inline prism binocs! Took me quite a bit of head scratching to work out how the modern binocs worked and came apart, but once I had discovered the functions of the various screws, it wasn't that difficult. Again, the most fiddly thing was getting both sides to slide together as one turns the finger screw. I still have to give one side a bit of a tug to be able to make full use of the eye adjustment, but I can live with that.
Cheers,
S[Here's a link to the Wikipedia discussion had on the topic back in 2007: I never did get around to hunting for the materials at the time, but I notice a few more details have been added since my last look:
Beautifully put, saves me the trouble of elaborating!
Andy
I haven't seen anyone recommending it. However if you have to, you have to.
No, they're a piece of piss. They're designed for easy mass production and they're not particularly sensitive to mis-alignment anyway. 10=D7 magnification? It's hardly rocket surgery.
Apart from, I think, a huge pair of East German border guard jobbies, I've not seen any binoculars that were adjustable to collimate anyway. The lenses are centred, and the rest is down to trusting the lens mounts to be machined accurately. Re-assembly is just the reverse of dismantling.
Besides which, what does "collimate to more than one person." mean? Collimation is collimation, it doesn't vary between people. Even for your pointy little head.
Lidl binos can be collimated, they have various adjustments. Most are the same, you just don't have a clue what to look for or what it means.
Google for conditional collimation and you might learn something to fit in you flat, empty head.
FFS! So that's where all the hi-fi nutters went.
"Conditional collimation" is nothing of the sort, nor is mutual collimation. It's _alignment_ (and important, I'll grant) rather than collimation. A chorus of screaming fuckwits doesn't make it so.
Collimation is the alignment of an optical system, such that everything with an axis that cares about it is aligned to the same mutual axis. Often (but not always) this is for the purpose of producing collimated (i.e. parallel beam) light. This isn't always needed, as not all systems are trying to achieve such light, but you won't achieve the second without the first. "Alignment" also means both angular and sideways displacement (although plane elements don't care about sideways shift).
In binocular terms, there are two optical systems and they don't interact (outside of nerves in your head). Each system is thus collimated separately. There is no mutual collimation, no conditional collimation. Collimation is also objective - the system has an ideal collimation (which in most cases is just "everything straight down the middle" and there's no "tuning" of this to a subjective use, i.e. the best collimation is the best collimation, there's no "setting it up for Fred".
There's one case where this doesn't apply - spectacles. That system is quite crucially your eyeball and the spectacle lens, collimation being dependent upon the frame and even the nosepads. This is why an optician who gives a damn about measuring IPD (interpupillary distance) is so important and why you shouldn't go to Specsavers.
Collimation is achieved in most optical systems by making accurate components and putting them into accurate lens holders. If the optical centre of a lens is in its geometric centre, and the lens holders are accurately made in the lens tube, then it all just works out fine. This has several benefits - fiirstly it's obviously cheaper (than adjustable lens mounts), secondly its better (the accuracy of doing it this way in modern production achieves better than most adjustment processes will), thirdly (and most importantly) it's more robust: binoculars get dropped.
Collimation obviously goes to lunch when you dismantle binoculars, so getting them back together afterwards is indeed an issue. Hopefully though (and this is true for everything small and cheap) it's a re- assembly task onto static marks. As discussed, binoculars avoid collimation adjustments for the sake of robustness. If you have any, the first place they'll appear is around the prism. This is because prisms aren't as easy to self-align as a simple Gallilean telescope tube. Even then, you're not going to see adjustments here unless you're dealing with three things simultaneously: high quality, high magnification, fixed mount. "Field" binoculars avoid adjustments.
Alignment is important, as the suggested web sources point out (the Oberwerk videos are pretty good). However this alignment is about the "fit" of the binoculars to the user's eyes and, in the extreme cases, about the relative alignment of the two halves of the binocular. This isn't collimation though.
Once again, field binoculars avoid this stuff where they can, because they're better off with robustness than with factory perfection.
The best "adjustment" for alignment is in the brain. We're good at this. If the binoculars are low magnification, you can stare at any old rubbish and the brain sorts it out. It starts to be more important though if any of the following apply: high magnification, dark images, long times staring through them, fast moving targets, particularly for acquisition of new images with tiny targets. I've just had a look at my collection and the only binoculars with a really comprehensive alignment system are a pair of ex-RN fixed mount ones that are quite low mag (about 7=D7) and came off the optical tracker pedestal from a Seacat missile launcher - Fast moving acquisition.
Alignment here is mostly around setting the IPD right, which you have to do each time you get them out of the case (and why I always carry my own pair, because my own sight is asymmetric, a bit crap, and a pain to adjust for). User handling at the time of viewing is still the biggest deal in getting a good image, not faffing about over minutiae. If you're using high magnification or staring for ages, you also need to align the axes carefully. This is usually done (if possible) by looking for adjustment setscrews between the lens housing arrangements (a pre-collimated tube that we don't mess with) and the hinged frame of the binoculars. They're sometimes hidden under the rubber grip. Then follow Mr Oberwerk, who explains it pretty well. He also refers to it as "Alignment (collimation)" throughout his vid.
What have opera glasses got to do with binos? Why introduce them here? You do know that a Galilean telescope doesn't use optics the same as a set of binoculars? Except maybe a few "focus" free models and opera glasses.
As I said you just don't know where to look. I will give you a hint, they are aligned in the factory by hand which is why Chinese stuff is cheaper, the hands cost less. If you look you may even find some alignment marks on the lenses put there so they could be assembled after testing. Of course they only allow for alignment in one axis.
I haven't seen anyone recommending it. However if you have to, you have to.
No, they're a piece of piss. They're designed for easy mass production and they're not particularly sensitive to mis-alignment anyway. 10× magnification? It's hardly rocket surgery.
Apart from, I think, a huge pair of East German border guard jobbies, I've not seen any binoculars that were adjustable to collimate anyway. The lenses are centred, and the rest is down to trusting the lens mounts to be machined accurately. Re-assembly is just the reverse of dismantling.
Besides which, what does "collimate to more than one person." mean? Collimation is collimation, it doesn't vary between people. Even for your pointy little head.
Not sure what is meant by collimation here (usually associate this with microscope light sources), but, without my glasses on I do find there is not enough adjustment on one of the eyepieces to correct for the difference in my eyes: so maybe that is what is meant. I can usually find a way to tweak the length of one ocular a little though.
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