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Glass types in NL Pure-series (1 Viewer)

dries1

Member
Reading this thread reminded me that just very recently the major binoculars manufactures, due to rush in competition started developing the binoculars that is overall optimized on all the critical features: FOV, Eye Relief, sharpness, color renditions, 3-D effect, Waterproof, etc....Step back 10 years, it was hard to find a binoculars that would overall optimized on all features: they were either short eye relief, narrow FOV (Leica, Votex...) or weird 2-D flat view (EL SV, EDGE,..) It's a long way to come up with recent products like NL Pure, SF x32.
IMO I don't think there has been a significant change in overall performance in the last 10 years. I have handled many a premium glass made from 2000. By the way both the SF and NL are flat views like the SV or the EDG, just done a bit different.
Granted the FOV has increased and started with the SF in 8 and 10X42 a few years ago, and the EII which I enjoy has always had almost 9 degrees FOV. If anything, the ER has increased for the benefit of those who wear glasses.
 

Robert Moore

Well-known member
The transparency of the image and contrast to me is what sets the NL apart from the rest. I wish I had the 8x42 Noctivid to compare the two.
 

jring

Well-known member
Mal,

Consider Schott as Shell. Your car drives on its fuel but does the same on Texaco, BP etc as long as its product has the same specs.
What kind of dopes they use in that fuel is nice to know for each company but of no concern for the driver. Its how the car drives that matters. Marketing slogans in the fuel industry can be read in the optics industry as HT, HD, Ultra HD, ED etc etc.
Schott, Hoya and all the other glass industry have catalogs which one can order. Read these and you know what's available.

Jan

Hi,

we will never know what glass is used in the new NL Pure series, unless either:

- Swaro publishes what types were used in which lenses

- somebody with access to an optical lab and the knowledge how to use it gets a pair of NL, rips it apart and starts to go to town with the bits... which might have happened already somewhere... but those in the know won't talk either...

For starters, you could measure the objective and eyepiece separately in an interferometer and determine the length of glass path of the prisms (for SA correction as glass path introduces SA).

Then measure specific weight of the glasses used for each lens as this gives a good hint at possible candidates and together with the knowledge of an experienced designer, one could probably start to simulate possible solutions in an optical design software and compare simulated results to the measured ones until you get a good fit.

As for Zeiss glass only in an instrument - that will be quite difficult, the norm is to use whatever is available and is a good match of design requirements and budget.

When talking about glass makers, Ohara should not be forgotten... their ED glasses do enjoy a nearly mythical reputation in the astro scene... here is the link to their catalog download page.


Joachim, who would put his money on a tuned eyepiece design to decrease lateral CA... do we have x-rays of the NL?
 

jring

Well-known member
Hi,

thank you for the x-ray link - yeah, they look similar enough. But since the x-rays are indeed quite similar and we have a wider field and observed less lateral CA, an element made from some special glass in the EP is possible...

Joachim
 

Binastro

Well-known member
Hi,
I haven't been following this thread, just the last few posts.

It is easy to measure curves and refractive index of glass.
One can be almost certain the Chinese and others buy new instruments, measure them and use the information to make clones if the market is there for them.
The do not care about intellectual rights at all.

The best glass companies like Schott have consistent high quality glass. They can be relied upon, although mistakes do happen.

Some of the Chinese glass is all over the place and needs to be repeatedly returned until the correct glass is made.
The main advantage of Chinese glass is usually only money. It is cheap.

There are indeed high quality Chinese products, but usually a Western firm is heavily involved in the manufacture and quality control.

My Canon A720 IS cameras from 2007 are Japanese but assembled in China.
Several have taken over 100,000 single exposures. One is on 175,000.
The success rate is 90%, compared with 60% from AI cameras.
The earlier Canon A 710 IS is made in Japan.
I suppose Canon just moved the necessary equipment to Canon China for the Canon A720IS.

Regards,
B.
 

GrampaTom

Well-known member
United States
Hi Joachim and Jan,

See the two x-ray images that mnich (as he's known here on BF) provided to Arek at Allbinos:
Optical construction of Swarovski NL Pure binoculars - AllBinos.com


John
thank you for the x-ray link - yeah, they look similar enough. But since the x-rays are indeed quite similar and we have a wider field and observed less lateral CA, an element made from some special glass in the EP is possible...

Joachim
Seems like maybe there's a missing part of this conversation? The number and location of lenses is one potential. The quality of glass and coatings being asked about here, is another. What about lens shape, curve, something the Xray view will not reveal? The offset from central axis of the SP prism in the NL suggests that to get the EP view concentric to the objective and ocular required some innovative grinding/shaping, if I understand this. What else of this ilk might be here?

G'Tom
 

GrampaTom

Well-known member
United States
I suspect it's not just diameter. Its the lens curvature, (a variable) and its location, (another). Thinking about the Xray view of the offset prism, are lens curvatures offset to correct for what seems a slight bent light path from the prism?

How can we scale to measure curves, especially if the idea of offset is valid from an Xray view taken at some angle to the whole, given its length? Anybody know what the dims and tolerances are for lens curves? .000X, .0000X, .00000X?

You know what they say about assumption.
 
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Maljunulo

Well-known member
I suspect it's not just diameter. Its the lens curvature, (a variable) and its location, (another). Thinking about the Xray view of the offset prism, are lens curvatures offset to correct for what seems a slight bent light path from the prism?

How can we scale to measure curves, especially if the idea of offset is valid from an Xray view taken at some angle to the whole, given its length? Anybody know what the dims and tolerances are for lens curves? .000X, .0000X, .0000X?

You know what they say about assumption.
There may be a problem of perspective since the x-ray source is likely to be a point, and unless it is at infinity (unlikely) the rays will be divergent, I think.

I'm just playing in my head here.
 

Binastro

Well-known member
I will find out what the tolerances for lens curves are for lenses, binoculars, spotting scopes and astro scopes.

I suspect around one part in a thousand.

There are tolerances also for wedge, thickness, rerfractive power, centration etc.

However, a true expert will adjust the spacing of components to correct for tolerances.

Top lens makers do this.

Regards,
B.
 

sillyak

Well-known member
I suspect it's not just diameter. Its the lens curvature, (a variable) and its location, (another). Thinking about the Xray view of the offset prism, are lens curvatures offset to correct for what seems a slight bent light path from the prism?

How can we scale to measure curves, especially if the idea of offset is valid from an Xray view taken at some angle to the whole, given its length? Anybody know what the dims and tolerances are for lens curves? .000X, .0000X, .00000X?

You know what they say about assumption.


The tolerances for lens curves are less than a wavelength of light. That is why they are polished so finely to final figure. Lots of information available on telescope making forums. How those curves are tested, measured and figured.
 

jring

Well-known member
Hi,

obviously we can't recreate the optical design just from the x-ray. I already gave some hints on how one would go forward to do so...

As for the curves, they can me measured with a spherometer as Binastro pointed out. As long as they are spheres - which is very probable for a mass produced refractor (lens telescope as opposed to mirror based) with glass lenses (as opposed to plastic - those are fairly easy to make in asperic curves).

One problem lies in the cemented groups, these need to be separated in order to measure them. For glass types, refractive index and specific weight are fairly easy to determine for separated lenses.
Other properties like Abbe Number or relative partial dispersion less so, but refractive index and specific weight give a small number of possible candidates.
Along with the knowledge of the radii and the position of the lens in the instrument, one can let the design program optimize the glass for best result, spit out a list of possible candidates from its glass catalogues and check which one fits regarding specific weight.

Joachim
 

wllmspd

Well-known member
You are only going to get very gross info from the X-ray, though X-ray “density” can give info on high atomic number recipe glass. You can bet they’ll be using the highest quality grades of whatever they are using, the design will use whatever dispersion material is needed. I wouldn’t try measuring curvatures or thicknesses with any accuracy. I would also note that quality of the polish of the lenses is also important and that will be “secret sauce” from whoever is making them. AR coating is also a black art, but with trade offs depending on what the company is most keen to address. Baffling and internal blackening will also play a role too…. Many parts to the package.
Peter
 

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