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Real calcium fluorite in NL binoculars? (1 Viewer)

Robert Moore

Well-known member
B&H says that the NL has fluorite containing HD lenses. On the EL it just says Flouride glass. Just wondering if it’s real fluorite like the Takahashi telescopes.
 

henry link

Well-known member
I just checked with a green laser. The objective elements are all glass - no Fluorite. However, I have found that the corrections for both longitudinal and lateral chromatic aberrations are exceptionally good in the 8x42 NL, I believe the best I've seen in a binocular.
 

Robert Moore

Well-known member
My Zeiss SF looks like it has a true Flourite element in the rear objective glass. Front glass has a dot with line and another dot and than no line and just a dot.
 

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henry link

Well-known member
My Zeiss SF looks like it has a true Flourite element in the rear objective glass. Front glass has a dot with line and another dot and than no line and just a dot.

Hi Robert,

I think I do see a barely visible wisp of a trail in the back element of the cemented doublet. You would expect a very dim trail through the "FL" glass and in this photo it's further obscured by the bright interior background. The front element has such a bright trail because it's a high dispersion "flint" glass.

In the photo below of the NL's air spaced triplet I tried to keep any bright light except the laser out of the binocular, so the dim trail through the front singlet and the "ED" element of the rear cemented doublet can be clearly seen. In this case the "flint" with the bright trail is the last element.

If they had gone to the expense of using genuine Fluorite I don't think Zeiss would have been shy about letting us know.

Henry
 

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Robert Moore

Well-known member
Thanks Henry for the info. You are correct and I checked it again with the laser. The rear element in the Zeiss shows a faint line but not completely invisible like in fluorite.
 

henry link

Well-known member
Thanks for the confirmation, Robert.

For small, low magnification binoculars I don't think there is much reason for anybody to use Fluorite or an equivalent glass type with an Abbe # of 95. Of course, that won't prevent the use of loose marketing terms that imply the use of Fluorite.

Henry
 
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GLOBETROTTER

Well-known member
Thanks for the confirmation, Robert.

For small, low magnification binoculars I don't think there is much reason for anybody to use Fluorite or an equivalent glass type with an Abbe # of 95. Of course, that won't prevent the use of loose marketing terms that imply the use of Fluorite.

Henry

Kowa claim on their genesis binoculars to use pure fluorite
 

binomania

Well-known member
The subtle distinction between (calcium) fluoriTe and fluoriDe (glass)...

Hi, here's
an excerpt from my old review regarding Kowa Prominar 8.5x44
(by google translate..sorry)

Mineral fluorite

The fluorite mineral is a halide of the monometric group has a hardness equal to 4 a specific weight: 3.1-3.2 and a refractive index: n = 1.433, it emits light when heated or exposed to ultraviolet radiation. It seems that its name may derive from two factors, first of all from the Latin fluere = to melt (since it was used as a flux in metallurgy). However, it seems that in the Middle Ages, the English miners mentioned it as Flower "FIORE" because of its beauty. Natural fluorite includes traces of rare earth elements that give the stone a purple or greenish color and cause, as anticipated, a fluorescence when subjected to heat or ultraviolet rays.

Synthetic fluorite by KOWA

The fluorite (fluorite crystal), used for the Kowa High Lander Prominar 32 × 82 BL8J3 series glasses and on the TSN-883/884 spotting scopes, is instead an artificial mono-crystal, for this reason, it does not contain impurities and does not emit fluorescence when Furthermore, when heated or exposed to ultraviolet rays, artificial fluorite is chemically stable, on the other hand it is more fragile than the mineral one and tends to scratch easily. For this reason, its processing is more difficult during the grinding and polishing phase, but it is possible to create large diameter lenses.
 

John A Roberts

Well-known member
Australia
For convenience, the main information from Dennis' link to the Kowa website . . .


John
 

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AlanFrench

Well-known member
Thanks for the confirmation, Robert.

For small, low magnification binoculars I don't think there is much reason for anybody to use Fluorite or an equivalent glass type with an Abbe # of 95. Of course, that won't prevent the use of loose marketing terms that imply the use of Fluorite.

Henry

Agreed.

Clear skies, Alan
 

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