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Are Tele Vue JAPAN circle NJ Plossls of 5 Element Design?

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#1 Stan Lopata

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Posted 30 June 2020 - 12:58 PM

Are early 1.25" Tele Vue JAPAN circle NJ Plossls of 5 Element Design??  That's my whole question.

 

Thanks,

Stan



#2 sg6

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Posted 30 June 2020 - 01:58 PM

Not sure but I would doubt it.

BillP may be along to give a greater depth of knowledge.



#3 Jon Isaacs

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Posted 30 June 2020 - 02:31 PM

NO... 

 

Jon


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#4 John Huntley

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Posted 30 June 2020 - 03:36 PM

This is from the patent for the Tele Vue plossl dated 1984. It is in the public domain:

 

 

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#5 j.gardavsky

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Posted 01 July 2020 - 03:12 PM

... and the formula is symmetric according to the text.

 

So, the patent is basically circumventing the Carl Zeiss Jena "symmetric Plössl", where the field lens and the eye lens are convex out, contrary to Tele Vue Plössl with the outer lenses concave out.

 

On my 6" F/5, the Zeiss offers more contrast but less AFOV, the Tele Vue is behind in contrast but it offers more AFOV. With the eye lens concave out, the Tele Vue Plössl can be better protected against the stray light reflections, coming on the EP around the observer's head.

 

Best,

JG


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#6 BillP

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Posted 01 July 2020 - 05:47 PM

NO... 

 

Jon

What Jon said.  Just the standard TV patented Symmetrical.


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#7 BillP

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Posted 01 July 2020 - 05:50 PM

... and the formula is symmetric according to the text.

 

So, the patent is basically circumventing the Carl Zeiss Jena "symmetric Plössl", where the field lens and the eye lens are convex out, contrary to Tele Vue Plössl with the outer lenses concave out.

 

On my 6" F/5, the Zeiss offers more contrast but less AFOV, the Tele Vue is behind in contrast but it offers more AFOV. With the eye lens concave out, the Tele Vue Plössl can be better protected against the stray light reflections, coming on the EP around the observer's head.

 

Best,

JG

Thanks for pointing this out. waytogo.gif   I feel that most think that it is simply the coatings used and internal baffling that increase contrast, but as you point out it is also the very nature of the optical design and the lens curves that do as well.  Some designs are inherently higher contrast and stray light controlled than others.


Edited by BillP, 01 July 2020 - 05:51 PM.

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#8 25585

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Posted 02 July 2020 - 09:53 AM

... and the formula is symmetric according to the text.

 

So, the patent is basically circumventing the Carl Zeiss Jena "symmetric Plössl", where the field lens and the eye lens are convex out, contrary to Tele Vue Plössl with the outer lenses concave out.

 

On my 6" F/5, the Zeiss offers more contrast but less AFOV, the Tele Vue is behind in contrast but it offers more AFOV. With the eye lens concave out, the Tele Vue Plössl can be better protected against the stray light reflections, coming on the EP around the observer's head.

 

Best,

JG

The "improved" design shortens eye relief. My CZJ 25mm is "standard" I think, useable with glasses, TAL better still better so. TV 25mm & Meade are unusable with glasses. 

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Edited by 25585, 02 July 2020 - 09:58 AM.

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#9 j.gardavsky

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Posted 02 July 2020 - 10:36 AM

The "improved" design shortens eye relief. My CZJ 25mm is "standard" I think, useable with glasses, TAL better still better so. TV 25mm & Meade are unusable with glasses. 

The TAL Symmetrical is a derivate of the CZJ symmetric Plössl, possibly a transfer from CZJ to TAL, and adapted for the LZOS glass standards.

 

The CZJ symmetric Plössl is available from some (military?) surplus

https://www.ebay.de/...1&hlpv=1&cond=1

and this is the pair I have. The glass is crystal clear.

 

Best,

JG



#10 25585

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Posted 03 July 2020 - 04:15 AM

The TAL Symmetrical is a derivate of the CZJ symmetric Plössl, possibly a transfer from CZJ to TAL, and adapted for the LZOS glass standards.

 

The CZJ symmetric Plössl is available from some (military?) surplus

https://www.ebay.de/...1&hlpv=1&cond=1

and this is the pair I have. The glass is crystal clear.

 

Best,

JG

Same as mine. They are a great bino viewing pair.


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