Opaque and greenish view (3 Viewers)

[Ignatius]

When looking through binoculars from the first quarter of last century and finding the view blocked by opaque and greenish lenses somewhere in the optical train, does that mean the canada-balsam has deteriorated?

 

[Foss]

Not necessarily. Can you post photos?

 

[Ignatius]

Viz. exhibits A, B, C and D courtesy of fleabay seller retro.audio










PS. I have bought it anyway and I shall attempt a salvage which will be documented and which I may possibly post here.

 

[Foss]

My guess is prism staining due to prolonged moisture intrusion, though it may well be something different. In photo #1, I see what I believe to be a prism chip at the 10 o'clock position.

 

[Ignatius]

Could than not be a 'bubble' where the achromat is separating?

BTW: it is a 1915 Carl Zeiss Wien Feldstecher 6fach M 9/13 Z with a dated Übernahmekommission engraving from 2.11.15. These are the same as Silvamars. In Seeger's blue book it is discussed on pp. 478-481. Serial 519144.

 

[pat mitchel]

I'd also use some light coming through the eyepiece while moving it around the EP and taking the same look through the objective. A small light source that can be placed to the objective and moved about may also aid in the diagnosis. Always better for the doctor to know pertinent info on the patient. Good luck! Pat

 

[Ignatius]

Ok. Any recommendations regarding grease for the IF's re-assembly after cleaning?

 

[pat mitchel]

Nyogel 767A in the US. As to local availability, I don't know.

 

[Ignatius]

We seem to only get 760G here, which I believe is a contact grease.

 

[pat mitchel]

I don't have any specs or even the knowledge as to what a "damping grease" is in comparison to other forms of grease. But a helical thread has a large contact area and that would seem to me to work against a thick grease. This might provide ample range of thickness

Helical Grease #500 15ml Made in Japan | eBay

Use best Helical Grease for your lens! Helical Grease are manufactured in Japan. 100% Made in Japan Degree of viscosity : #500.

www.ebay.com

 

[Foss]

With no firsthand knowledge, I've heard of Nye Fluorocarbon Gel Damping Grease being used with success.

 

[Ignatius]

@pat mitchel : Someone else recommended that helical grease, but #3000 with a viscosity index of 270.
@Foss : Nyogel 774H with a viscosity index of 289 was suggested by someone.
Both those tips came from another bino forum. #500 grease has a viscosity index of 260. Seems like the answer will lie somewhere in that range then, 260 - 289. Apparently that range has a JIS & NLGI number of 2, which according to a wikipedia entry on the topic makes it as gooey as peanut butter ...

Silicone-based or lithium grease?

 

[pat mitchel]

this off the net
"It's not advisable to use them on plastic parts. As lithium is based on petroleum, it tends to speed up the decay of rubber and plastic components. Lithium-based grease can withstand high temperatures and are perfect for cars, heavy machinery, and guns."

What are the differences between white grease, lithium grease and synthetic grease?

Answer (1 of 2): There are many different greases and they all suit different purposes. The white greases I have seen used are on anything remotely to do with food production. Normal oils and greases are poisonous to animal life. Lithium greases are normal everyday, nothing special greases. Mo...

www.quora.com

Pat

 

[Ignatius]

Ok. So the answer that appears to crystallize ist a NLGI2 silicone grease with a viscosity between 260and 289. I shall see what is available here.
Thanks to all for their input. The patient is en route and I expect next week to be exciting.
Here are a few more pix from the seller:

 

[LPT]

Look carefully at the pictures of the eyepieces. Note that there are filter cups installed on each eyecup. This will account for a great deal of the lens colouration. Also, the photographs have an excessively green colour balance distorting the actual appearance of the binocular. So I’d say those are yellow or orange filters.

 

[Foss]

^^^ what he said
@ Ignatius: The UK prism stamp and symbol are intriguing. You've got yourself a real gem there.

 

[Ignatius]

Yup. I can see where he's coming from. I hope he's right, because that could possibly mean a lot less of a hassle. I am just reading up about the use of filters for binos back then in the blue book.
The Ü.K. stamp is from a military agency responsible for purchases for the artillery as I understand it. According to the blue book the stamp dates release of the binos to the troops, but it does not necessarily correspond to the serial number. Often the Ü.K. date is between 3 months and a year after the production date. The symbol is the double-headed eagle of the Austro-Hungarian empire. It was used for that purpose until sometime in 1916 from when the 'Allianzwappen' was used. That thing in itself is a complicated symbol to understand consisting of three coats of arms: the Austrian one and the Hungarian one connected in the middle by a small Habsburg one.

I am in the process of finding out whether the current agency has anything to do with that. Apparently an agency of this name was already in existence in the Napoleonic wars. The Swiss seem to have something of that name, too.
Cannot wait to hold it in my sweaty little paws.

 

[LPT]

This is mine. Optically in fine condition with a nice view. Note the brass eyecups. The Ü.K. stamp, though, is in poor condition. Yours is superb, far better than average.

 

[Ignatius]

Nice one @LPT - a 6x24 afaik. I wonder whether the stamp was partially obliterated to 'de-militarize' it?

 

[LPT]

Yes, a 6x24. Symbol has been rubbed but if examined closely under a strong light it is still entirely visible. Obliterating Nazi symbols I can understand but this one not so much. Even with the marking obliterated it is obviously still a military binocular.