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Fuzzy prism (1 Viewer)


Dundee Birding....(target 150 in 2024).
Had an APO Televid 77 scope which didn't seem to be working as well as it should be when I tried it - having never really used it after buying it 2nd hand. The front lens coating was visibly damaged and reading up on old threads on here suggested that this could cause problems but was fixable, so having emailed Leica I sent off the scope for repair. Today I received a message from Leica which highlights that another problem has been found by them.

During our initial control we noticed that the prism is foggy. Unfortunately we are not able neither to exchange nor to clean it due to the lack of spare parts. This will remain unaltered after the repair.

I don't know how much this problem would affect viewing through the scope - perhaps this was the actual cause of the problem? I was hoping to be able to sell the scope on after repair (having replaced it with a newer model scope) but if this "foggy prism" is the main issue then it is likely to be a waste of money getting the repair done. Google hasn't been much help in ascertaining how much of a problem (and exactly what sort of problem) this is likely to be.

Any explanation as to what problems this might cause, or as to whether it is worthwhile going ahead with the original repair given this can't be fixed, welcomed.
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A foggy prism could be moisture affecting the surface.
Sometimes it can be cleaned.

However, if the glass has actually been affected, say devitrification, it may be deep.
Sometimes an expert would repolish the prism, usually a skilled amateur telescope maker.

Some firms will not deal with fungus, if that is the problem.
Zeiss are reputed not to be prepared to deal with this in lenses, but they did an excellent job with a 15x60 binocular.

Photos of the prism would be useful.

It may be this scope has to be written off or used as is.

Is the repair to the objective free or low price?


You could try East Coast Binocular repairs to see if they have replacement prisms.

If what is needed is just repolishing the surface then it might remain uncoated, but this shouldn't be too bad if one surface is involved.

I don't know if there are cemented prisms here and the cause is balsam failure?
Even here a skilled telescope maker would separate components and recement.

Personally, I would leave things as they are, as I don't have the energy nowadays to pursue problems.
But if one has the stamina it could be worth pursuing.

However, is this cost effective?
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Thanks, Binastro. Repair/replacement to the objective lens is gonna be roughly £160 - which is a lot of money to write off if the scope isn't gonna be particularly improved. By the sounds of things from Leica the actual prism is affected in some way and Leica do not have any spare parts to replace it.

I have recently bought a replacement scope and was hoping that I would be able to recoup some of my considerable outlay by selling on the Leica once fixed but getting a buyer (even just covering the £160) for a scope that works, but not brilliantly, is highly unlikely. I've asked Leica for more info so hopefully I will get some idea from them as to whether or not replacing the objective lens is gonna make enough of a difference to be worth the outlay.

Ask Leica what the problem is with the prism.
Is it surface damage or deeper?

Is the eyepiece damaged?
If not, then it has a value and only the body value has to be considered.

I think this problem is all moisture related.

Leica have replied and said that it is relatively light fogging (some moisture has got in apparently) and that it is unlikely to be noticeable when using the scope, so I've gone ahead with the repair.

Thanks again for your help. Much appreciated.
Hope it works out.

Leica will, I suppose, put nitrogen gas back in, but it might be advisable not to use the scope in wet or very humid conditions.

I suspect that the technician will lightly clean the prism outer surfaces.

Also the scope should be stored in conditions above 13C and less than 60% relative humidity.

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