Binoculars - adjusting prisms

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davidej

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I dropped my Tasco Offshore 7 X 50s and now I get a very noticeable double image -enough to really make them unuseable.

I have searched the internet for instructions to adjust them but without much success. So I have taken out one eyepiece (this seem to be the only part I could dismantle) which reveals two screws which I take to be the adjustors for that prism. However screwing them in and out does not seem to have any obvious effect.

Does anyone have any suggestion how to proceed from here - getting them done professionally would cost as much as replacing them.

Thanks

david
 
given that you might have to adjust - and check that adjustment - in three dimensions, I think that you are on to a loser. Perhaps we should all ask what is the real advantage of binoculars - you don't use three D vision through them, anyway.

I have a couple of excellent 7x50 monoculars made from a similar pair of bins. Monoculars have a tremendous advantage: you can use them with one hand, and keep one for the ship; they are also lighter. If you fit one of them to a pistol grip shaped piece of wood, it's even easier to handle - but perhaps not in the vicinity of a US Navy vessel !
 
when i did this to my binolculars i also took them apart and found that the shift in the prisms was obvious as the locking paint was disturbed. I simply moved it back to as close as possible and put a spot of quick setting epoxy on.
I also put some on the other lock on the other eyepiece.

Not much help i know but you may have taken the wrong eyepiece apart.

Steve
 
You need a calibrated optical bench to do this properly. We used to do these at work back in the 60s but by 1980, we'd removed the facility as it was cheaper to replace the binoculars. Now you can buy a good pair from Aldi/Lidl for around £30.00, I think you'd find it uneconomical, even if you could find someone to do it.
 
davidej

I would suggest the first thing to do is unscrew the eyepiece and then, very carefully, screw it back on again, making absolutely sure that the screws are engaging where they should and not where they might have ended up, dislodged, after the drop. I did this after trying all the posted suggestions and hey presto, five minutes of thumb and forefinger achieved what two days of sweat, swearing and threats could not. Failing this, bite the bullet and consult Aldi or Lidl...cheaper!
 
Almost certainly you have displaced one of the prisms. Removing and replacing the eyepiece will not help. It is possible to get most binoculars professionally recollimated but as has been said by others, this requires an optical bench set-up. You can find optical repairers by Googling.

I recently repaired mine by completely dismantling them and found that one prism had moved in its mounting. Simply replacing the prism improved things dramatically and they are now usable. If your binoculars cannot be disassembled, then I fear you've had it.
Morgan
 
I had this happen to a cheap old pair of binos too. Given that they were a write off, I give 'em a good hard bash on the opposite side & got a few more years out of them.

I currently carry a couple of cheap pairs aboard & as soon as one pair goes belly up, I will buy a replacement when I see a suitable bargain. So far they seem to last about 10 years or so - about £3 a year. I couldn't live long enough to get that sort of value out of an expensive pair - and would probably drop 'em overboard anyway.
 
davidej said:
I dropped my Tasco Offshore 7 X 50s and now I get a very noticeable double image -enough to really make them unuseable.

I have searched the internet for instructions to adjust them but without much success. So I have taken out one eyepiece (this seem to be the only part I could dismantle) which reveals two screws which I take to be the adjustors for that prism. However screwing them in and out does not seem to have any obvious effect.

Does anyone have any suggestion how to proceed from here - getting them done professionally would cost as much as replacing them.

Thanks

david
Click to expand...

While in the MN, the bridge binos got "dislodged" from where they were left, quite often. By dislodged, I mean dropped or sliding off when rolling.

I found that the main front lens usually got moved on its long fine threaded fitting. Have a look to see if it has been moved by looking at the body/lens join. If it has been moved, mark where the lens is in relation to the main body, and unscrew it. Then very carefully re-align the threads and screw back on. Don't try to force it. If the marks and body join don't line up, remove it and try again.

It worked for me a few times in re-aligning the bridge binos.
 
Binoculars

In my experience Euroe and Phillip Steveens have got the right idea. The lens more likely the front lens will be dislodged. Try unscrewing and refitting. good luck olewill
 
Tasco offshore

David the same happened to me. The Tasco offshore took a tumble and now have double vision. How can they be fixed? Were great binoculars.
I have tried unscrewing the lens many times.
 
Re: Tasco offshore

I wish to resurrect this thread. I am facing the same double-image issues with my trusted pair of TASCO MARINE binos and so far I have been unable to locate the prism adjusting screws.
Did anybody disassemble the beast who can provide some useful hints? I keep reading about peeling off th erubber armour but I hate to chase blindly a tiny screw that might as well be located somewhere else. Neither I was able to retrieve any information or assembly drawing that I can use for disassembling.

Thank you

Scud
 
The good news is that there is no need to peal off the rubber armor. Unfortunately, the rest of this post is all bad news. The prism adjusting screws on the Tasco Offshore OS54 and OS36 are next to the eyepieces under some plastic trim. These Marine Binos are a marvel in the use of cheap materials and methods in a product that works very well. That is until they are dropped. There are two prisms in each side and they are secured with a glue like material that is very brittle. This material cracks when the binos are subjected to sufficient G-forces. Adjustments to the loose prisms would be pointless. The metal springs left to hold the prisms in place will not keep the prisms secure. The glass chips you may see inside the objective end are most likely pieces of the larger prism. I have taken my OS54 with double vision apart and I am not excited about putting it back together.
One would need to remove the existing brittle glue and replace with a more flexible material such as silicone glue. This requires complete disassembly of one half of the binos and the resulting repair is likely to be an ugly and low quality piece that we would not want to use.
We live in a world of disposable goods. I recommend NOT buying the older Tasco Offshore binos on line as they are unlikely to survive the rough treatment in shipping. I have had two pairs arrive damaged by the USA postal service.
 
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