View Full Version : Optics repair advice needed

Charlie in Dayton
2005-Apr-15, 08:42 AM
(Author's note -- if you get this intense sense of deja` vu when reading this, you're not demonstrating paranormal abilities -- I've got this posted in several different places in cyberspace for maximum exposure.)

Well, I said, sezzi, sitting there late at night listening to the BBC World Service audio stream while guzzling a Diet Coke and noshing on a low-fat granola bar...someone out there knows how all this works.
The shipment of old binoculars finally arrived (and no, I'm not referring to the sets you may have seen me selling -- those are BRAND NEW, he said with the bonhomie of a pre-owned conveyance purveyor), and I went through large quantities of paper towels and glass cleaner for the bodies and official Zeiss lens cleaning towels for all the lenses. Surprisingly enough, they all cleaned up pretty good.
The little insurance company premium 4x30's are just toys, and will live out their days in the desk drawer as a just-in-case -- they're really not good for anything more than looking across the room to see what channel the TV's on. They're a simple straight-through no-prism design.
There's a pair of Bushnell Expos, which the web says are floating cheapo 8x30's. They work okay -- most likely they'll live, wrapped in an old threadbare towel, stashed in the back of the car in the travel milk crate. They're an oddball design -- independently focusable eyepieces, not connected in any way. Each ocular has its own thumbwheel, which is not that bad an idea -- each eye can be focused to sharpness without affecting the focus of the other. They're a bit dim, though -- daylight specials, it seems to be.
Next are two pair of 7x35's. One has a long focus wheel, and seems to have heftier prisms. They're more hand-filling, and look to be physically larger. They don't do too awful bad in the dark. The other set has the narrow 3/8" focus wheel, and the 'traditional' size/feel for this size. Both will get some semi-serious evaluating this weekend, and they may very well go into the bino box as loaners for show'n'tell.

And now we get to the reason for this little expostulation. The last set is a pair of Binolux 7x50's in relatively decent shape. The faux 'gator hide is only cracked in one small place, they fill the hand nicely, the heft is enough to lend stability, and the lenses cleaned up nicely. I might leave 'em in the back window in the sunlight to kill some perceived ickies inside. But there is one BIG problem...they're out of line.
When I look through 'em, my eyes feel like they're trying to swap holes. I can fight it, and with some adjustment of interocular distance things will eventually settle down, but I can tell that I'm gonna wind up with either one heck of a headache or a sprained eyeball eventually. The effect seems to more-or-less go away if I rock over to the right, so the bino tubes are one above the other instead of side-by-side. Looking at the binocular prism body where the objective lens case screws into it, on the left side you can see where the objective case isn't square into the prism body like the right side is. It's almost like someone unscrewed that lens case, and then when screwing it back in, they got it cross-threaded, so now things on the left side don't line up. I'm almost (note I said ALMOST -- not quite there yet) ready to take a deep breath, grab the objective lens, and see if all that will unscrew from the prism body, then try to screw it back together straight. I'm not really ready to send it to a shop for repairs, as I'm cheap, and if this is fixable at home, I'd like to try it. These binos seem worthy of saving -- using alternate eyes, they feel like a nice set that would do well for stargazing on a night when it's more fun just to go casual.
So...anyone got any ideas here? Does it at least seem as I may have a decent idea? Anyone know fer sure how to take these beasties apart? I mean, if they do come apart, may as well dismount as many lenses as safely as I can and clean everything...

Suggestions are earnestly invited...

2005-Apr-15, 04:36 PM
I don't think slight cocking of the objective will cause that sort of misalignment. If you hold a plain convex lens and look through it tilting it does not displace the image although it does distort it. I'm guessing they were dropped and the prism(s) are out of alignment. The objective was removed in an attempt to repair and then screwed back on crossed after no luck.

BTW, the eyepiece oculars on the Bushnell expos are very handy for making finder scopes.

2005-Apr-15, 06:32 PM
It sounds to me like you are correct. Somebody opened them and let the nitrogen charge out. That's why you are thinking of putting them in the sun to dry out the innards.

If the lens retainer is cross threaded you migh be able to get the threads "chased" at a local machine shop. Once the threads are clean, the retainer will probably go back on nicely.

Getting the lens back on and sealed may take hunting around for a new O-ring. Which brings us back to the nitrogen fill. I don't know how you're going to do that. If there is a Union Carbide, Air Liquide or other similar cryogenic air seperation plant near by, you might be able to take your Stanly thermos over and get some from them.

Rotsa ruck. :D

2005-Apr-15, 06:58 PM
I would also suspect the prisim mount is either misaligned or the prisim has be cleaned at sometime and not been reseated correctly. The cross threading shouldn't be too much of a problem unless the objective has been forced and the threads really mangled. Normally with a bit of care and a delicate touch you can get the threats to mate correctly. If all else fails you can always separate the two halves and use the good one as a mononcular and with the bad one dismantled you have a nice eyepiece and some optics to play with on a bench.

If you can get them repaired to your satisfaction why not purge them with argon? Most workshops will have a mig weding set around somewhere and an argon cylinder.

2005-Apr-15, 07:23 PM
Just to add.

As with any other precision mechanisim, before dismantling make sure you have an adequate workspace, time when you will not be disturbed, pencil and pad for notes and sketches and a tray with some small jars or whatever for holding screws (which are tiny). You will aslo need a set of watchmaker's screwdrivers. A white or pale coloured sheet spread on the floor is also a boon when it comes to looking for dropped items - trust me on this, I used to repair antique watches before the eyes deteriorated! Carefully note which way lenses and prisims are oriented even if you suspect they are wrong you need to be sure you have reversed them. To do this on glass items use a felt tip on a non functional part (eg. lens edge)Above all be careful and don't force glass items. Optical glass is very fragile and is easily chiped or scratched so have plenty of unimpregnated lens tissues handy to store items on your tray. If you can get them, cotton backed faux kid gloves (used in industry) are ideal for keeping fingerprints off cleaned parts yet still allow for some sensitivity in the fingers

Just treat the whole process logically and remeber if you start getting frustrated have a coffee break. Someone put it together in the first place so you should be able to dismantle it and put it back together again.

mike alexander
2005-Apr-15, 08:50 PM
And if you have a digital camera, take pictures as you go. Even better than drawings, and you can print them out and annotate as necessary. I use this method when cleaning the mass spectrometers and have been saved some incredible howlers by having an objective record.

2005-Apr-15, 10:24 PM
And if you have a digital camera, take pictures as you go. Even better than drawings, and you can print them out and annotate as necessary. I use this method when cleaning the mass spectrometers and have been saved some incredible howlers by having an objective record.
Beat me to it! Any time I'm repairing electronic, electromechanical, or mechanical equipment, those photos have often been real life savers.

Re the cross-threaded situation, try using an appropriate grade of wire brush to remove debris from both sets of threads, clean thoroughly, and then, with the two parts in mounting position, apply light pressure and turn the lens mount counterclockwise slowly until you sense a "click". If the threads aren't too damaged this will typically be the starting/entry point for the two threads. Stop right there while maintaining the light assembly pressure and slowly turn the lens mount clockwise. If things are going smoothly, have a solid feeling, and no sense of "sponginess", then the threads are properly mated and should have coaxial pitch diameters, giving the objective lens proper alignment.

Charlie in Dayton
2005-Apr-16, 05:07 AM
I'm reading all this with interest...
I've tried getting the lens case out of the prism body with no luck -- and lemme tell ya, there ain't a pickle jar lid on earth can resist when I'm in the mood for a kosher dill, so these things are together tight -- no movement at all. I can't get 'em apart, and even if I could, it sounds like the adjustments are beyond my experience. And I guarantee the inert gas purging is.

There's a major binocular supplier with a repair facility here in town, and the rates don't look that outrageous -- I'm thinking of having them take a look. If worst comes to worst, a hacksaw'n'file job so's I have a good 7x50 monocular ain't the worst idea in the world...

Yeah, it's possible they were dropped -- there's a humongous ding on the edge of the lens ring on the cocked side. I guess I'm gonna have to take y'all's word that the prisms are out of whack. It looks for sure like with one side cocked, they aren't pointing parallel any more, hence the headache.

Think I'll compose a suitable email to ask if they work on these old things, can I drop 'em off/pick 'em up, are they worth saving, etc etc etc...

Stay tuned -- this'n ain't done yet.

2005-Apr-16, 05:21 AM
Put a hose clamp on the objective retainer. Then use vise grips on the hose clamp to gain some advantage. It will loosen.

Charlie in Dayton
2005-Apr-18, 08:17 AM
Well, I have an e-mail in to the local repair center, and I'm checking for more on the Internet. I would kinda like to get these beasties fixed...

If I can't, though, the idea has been bandied about to take 'em apart and have a decent large-aperture monocular. Well, I've been thinking about that. Separately, each tube still works fine. I just can't get the images to properly work together. If I separate the tubes, that means cutting the supports at the focus wheel/shaft, so that the side I save will still have wheel focusing. But which side do I save? The 'cocked' side? The good side (which has the diopter adjustment on it)? I can cut the supports near the focus shaft with a hacksaw, and with a fine file I can smooth things down so there's no raw edges. The side without the focus wheel -- will the eyepiece just fall out of the body? Is there anything holding that eyepiece in at the end of its travel, so I can just push/pull on that side to focus? Heck, if the side that pushpulls is workable, I'll leave that down by the big scope at the museum, to use as a spotter...

Anyone got any info that might prove useful here?

2005-Apr-18, 10:44 AM
Any chance of some pics of the offending beastie? It would greatly help in trying to identify the exact problem.

Something else you could try, draw two circles round the eyepieces onto a sheet of white paper and do a sloar projection at some distace (say 1 or 2m) and see just how much anglar displacement there is beween the two section images. It's possible the frame and focussing adjuster are bent and just need 'coaxing' back into line.

Edit: My guess is that if you remove the frame from one or both sides of the optical 'tubes' then the objective and eypeice sections will just slide apart although there may be stops somewhere to prevent this.

2005-Apr-18, 03:15 PM
Charlie, I'm not sure it's worth spending too much time trying to fix them. I was just looking at an ad in a flyer for the Jysk store up here in Prince George for 10x50 fully multi coated binocs for $14.95 Cdn.

Charlie in Dayton
2005-Apr-19, 12:20 AM
Sorry about that, frog esquire, it'll be a couple months before there's enough spare mazooma for server space...car insurance, taxes, life insurance, all that there inconsequential stuff rears its ugly head in May...

Evan, I'd love to look at a web ad for those 10x50's even though I have a pair already...those ruby-lensed anti-glare cheapos aren't worth the colonic bip-residue it'd take to bury 'em when it comes to astronomy...

This set seems to be worth investing a few (operative word FEW) bucks in...at this stage I"m just investigating...otherwise, it's time for the hacksaw...