Carl Zeiss Jena reverse Porroprism Binocular. (1 Viewer)

Just found this tucked away in a drawer.

Possibly 6x15 Teletur, but markings are very faint. 1910 to 1924?
I think that someone has painted over the metal parts in black.

Objectives about 14mm aperture.

What surprised me is how good the image is.

Although uncoated there is one blue coated surface in the right barrel and one pale yellow in the left barrel.
This may be natural blooming or from the small amount of internal haze.

Close focus about 9ft for me.

It is dull now but will try it further.

Centre focus. brass? plates. Black leather covered body.

Although the right dioptre seems jammed, the eyepiece unscrews with a fine thread and I get good adjustment like that.

I may have the details wrong as the markings are so faint.

I may actually use this.

Regards,
B.

Picture, please?

Sorry Canip,
I don't know how to do pictures, but there are photos of the same model easily found on the internet.

The reason it was put away is that it needs overhaul as it doesn't focus correctly at a distance. The view is good indoors.

The binocular is indeed a 6x15 Teletur, early, as it is only marked 6x not 6x15.
I probably found it in a charity shop, thinking it looked Zeiss and it is.

What is interesting is that some of the hundred year old glass surfaces have a thin antireflection coating caused by natural blooming.
I doubt that anybody would have deliberately got this binocular coated.
It was I think Dennis Taylor who first understood why old camera lenses had better transmission than new lenses
in the early 1890s.
Photographers did get old uncoated lenses coated, and I did the same with two 120mm aperture telescope objectives.

Strangely, some photographers deliberately removed coating from coated lenses to get a dreamy effect.

Regards,
B.

I have just seen a note that Joseph Fraunhofer first noted antireflection coating in 1817 after using sulphuric acid on glass.

It maybe that Dennis Taylor's reference in 1891, in his work on testing telescope objectives, that natural tarnish is a friend not a foe, was something that was known to him and others much earlier.

This makes antireflection coating knowledge 200 years old not 100 years plus, if this account is accurate.
I wonder if this effect was known even earlier.

Taylor Hobson were chemically coating lenses in the early 1900s, but the coating was not very efficient.

B.

Hi Binastro,

Following on from my recent posts about the development of different prism types (at: https://www.birdforum.net/showthread.php?t=378895&page=2 ),
I’ve been spending some time looking at Zeiss’ early binocular offerings

Fascinatingly, they explored all sorts of possibilities/ combinations with a variety of commercial models up to WWI
Then in the 1920’s there were even more combinations, especially using roof prisms (but in the 1930’s following the world-wide economic collapse all this ceased)

For a quick entry point to the models, along with basic data, see the classic listing from Kind, Huderman et al. at: http://home.europa.com/~telscope/zeissbn2.txt
I’ve attached two tables based on the data:
- early Porro variations by Zeiss, and
- early roof prism models by Zeiss

As can be seen, the 3x13.5 Teleater of 1909 nominally preceded the 6x15 Teletur of 1910
Both used inboard Porro construction, and seem to have been Zeiss’ first centre focus offerings

For illustration, I’ve also attached, an image of:
- the Teleatur (from: https://www.antiquesnavigator.com/d...que-binoculars-opera-glass-cla-rosenthal.html ), and
- the Teletur (from: http://www.fernglas-vitrine.de/teletur_6x15.htm )

And more information and images can be found on the Vacani’s site at: https://www.binoculars-cinecollectors.com/html/body_ger_8_theater.html


John


p.s. a very interesting observation about Fraunhofer - is there a link to where you found the information?

Thanks John.

Two of those sites I also turned up.

The Fraunhofer comments came up as I was searching for early antireflection coatings.
It was a translation from German of Fraunhofer's own observations in his notebooks.
I don't remember where I saw it.

It seems that he was buried in a building collapse, somehow survived, and taken under the wings of an aristocrat. He was given an education, and found ways of producing large optical blanks. Eventually his crown glass was better and more consistent than the British glass, and he produced better glass than the British.
He was a genius.
As with many optical workers of the time he was exposed to heavy metal vapours and died at the early age of 39.
The comment about his observation was that where the sulphuric acid had been used on the glass blank the reflections were less than where the glass had not been affected by the sulphuric acid.
It may be that the theory was not yet known? Also how much sulphuric acid was needed, and whether it was permanent antireflection coating.

About 1884 Lord Rayleigh first noted antireflection coatings, with perhaps the theory.

In 1904 Taylor Hobson were chemically coating glass.

But it is possible even in the 1700s it was noted that older glass had a natural bloom.
Spectacles were first used perhaps in the 1200s?

With only single pieces of glass, whether they had a natural bloom or not is not significant.

Of my three 120mm identical refractors I cannot easily see which is the uncoated one and which coated.
Here there are 4 surfaces professionally coated.

Regards,
B.