91 replies to this topic

[Alan French]

Looking for natural fluorite for large apochromats. 

 

https://en.wikipedia...va_de_Naica.JPG

 

Clear skies, Alan

 

(For entertainment purposes only.)

 

 

Edited by Alan French, 12 October 2024 - 01:14 PM.

[M44]

I can see my future 22" Fluorite doublet, somewhere in there. 

[Phil Perry]

Large natural fluorite crystals are likely to be flawed, and very, very expensive. I would think that synthetic crystals would be much more flawless and a lot cheaper (as well as more uniform in their optical properties). Do optics even require a crystalline structure, as opposed to bulk (amorphous) fluorite? After all, glass is the latter.

 

(I ask about crystals, because you linked to a page on large crystals.)

[Alan French]

Large natural fluorite crystals are likely to be flawed, and very, very expensive. I would think that synthetic crystals would be much more flawless and a lot cheaper (as well as more uniform in their optical properties). Do optics even require a crystalline structure, as opposed to bulk (amorphous) fluorite? After all, glass is the latter.

 

(I ask about crystals, because you linked to a page on large crystals.)

All true. It was meant solely as a joke. 

 

I don't know the answer to your question, I could only speculate.

 

Clear skies, Alan

[Jon_Doh]

The ones I found had already been sweated on 

[quilty]

So another issue, bad smell?

Those flourite scope lenses, are they lab grown monocrystals or fused polycrystals?

[Lagrange]

So another issue, bad smell?

Those flourite scope lenses, are they lab grown monocrystals or fused polycrystals?

They're monocrystals grown in a vacuum furnace - Canon Optron have this summary of their process.

 

It's a slow and expensive process to grow the crystal plus the time needed to anneal it afterwards, which is part of the reason why fluorite lenses are relatively expensive.

 

The ultra-high purity fluorite made for things like lithography equipment is extremely costly. According to Corning a 12" diameter, 2" thick blank of their highest grade fluorite would cost in excess of $200,000.

 

When fluorite first started being used in the 1880s by Abbe and Zeiss, it was all sourced from a single mine in Switzerland which produced unusually large and clear single crystals. "Large" in this context means big enough for things like microscope lenses and eyepieces but were much too small for camera lenses or telescopes.

Edited by Lagrange, 13 October 2024 - 09:54 AM.

[quilty]

I'm not asking about Canon but usual scope lenses.

Your comments reveal the little suitability for hobby astronomers.
200k for half an 8" lens, maybe 100k for half a 6"? Thanks but no, thanks

And that cost reveal as well that such production takes much more of an effort than glass metltings do. Which was denied by someone in here.

So no real option for a hobby astronomer

Edited by quilty, 13 October 2024 - 10:08 AM.

[Mark9473]

I think your reading skills could be improved, quilty. ;-)

[Lagrange]

I'm not asking about Canon but usual scope lenses.

Your comments reveal the little suitability for hobby astronomers.
200k for half an 8" lens, maybe 100k for half a 6"? Thanks but no, thanks

And that cost reveal as well that such production takes much more of an effort than glass metltings do. Which was denied by someone in here.

So no real option for a hobby astronomer

Canon make the vast majority of fluorite lenses for refractors and always have. I wouldn't be surprised if something like 90 to 95 percent of all fluorite refractor objectives ever made were produced by Canon.

 

Nobody would use a $200k fluorite blank for an application as mundane and undemanding as amateur astronomy. That grade of fluorite is only needed for the highest possible performance in the deep ultraviolet. Also, cost doesn't scale linearly with blank diameter - a 6" blank would be a small fraction of the price of a 12" blank.

 

For something that's not an option for a hobby astronomer, it's pretty weird that this hobby astronomer owns three fluorite scopes despite not having a huge budget to play with.

Edited by Lagrange, 13 October 2024 - 09:02 PM.

[Jan-S]

Why are we shining lasers through fluorite scopes, to see if the rays disappear? We should be shining blacklights, and enjoy the spectacle!

[turtle86]

Why are we shining lasers through fluorite scopes, to see if the rays disappear? We should be shining blacklights, and enjoy the spectacle!

 

Very true!  My wife collects crystals and the fluorites put on quite a show under a black light.

[25585]

Is that an ultra violet light?

[Jan-S]

Is that an ultra violet light?

Yes, UV light. Where I live, that's often referred to as a "blacklight", especially if employed in a bar or so. Maybe I used the wrong term. "Blacklight" may be one of those terms that sounds English, but is not. Like saying "beamer" (in German or Dutch) for a projector, while in UK English that would refer to a BMW car (if at all a proper noun).

Edited by Jan-S, 15 October 2024 - 06:25 AM.

[quilty]

I think your reading skills could be improved, quilty. ;-)

please help. What didn't I understand?

[quilty]

Canon make the vast majority of fluorite lenses for refractors and always have. I wouldn't be surprised if something like 90 to 95 percent of all fluorite refractor objectives ever made were produced by Canon.
 
Nobody would use a $200k fluorite blank for an application as mundane and undemanding as amateur astronomy. That grade of fluorite is only needed for the highest possible performance in the deep ultraviolet. Also, cost doesn't scale linearly with blank diameter - a 6" blank would be a small fraction of the price of a 12" blank.
 
For something that's not an option for a hobby astronomer, it's pretty weird that this hobby astronomer owns three fluorite scopes despite not having a huge budget to play with.

Well, this is something I didn't know. Those Tak flouride lenses come from Canon.
And these elements, too are those single crystals grown in the lab.

Edited by quilty, 15 October 2024 - 06:38 AM.

[JeremySh]

 Those Tak flouride lenses come from Canon.
 

Fluorite! 

[quilty]

Fluorite!

They come from Canon, too?

[25585]

They come from Canon, too?

   

[quilty]

To those who have poor understanding

Some of you make a HUGE deal out of ou vs. uo as well as d vs. t.
I have the right to do the same, haven't I?

What if Canon do the very same and decide to produce fluoride lenses only furthermore? All those fracs have to be redesigned

Edited by quilty, 18 October 2024 - 03:04 AM.

[Lagrange]

To those who have poor understanding

Some of you make a HUGE deal out of ou vs. uo as well as d vs. t.
I have the right to do the same, haven't I?

What if Canon do the very same and decide to produce fluoride lenses only furthermore? All those fracs have to be redesigned

I presume you mean "what if Canon decide not to produce fluorite lenses?".

 

Given the usefulness of fluorite in a variety of applications outside of amateur astronomy and their significant investment and capability in this market, that would be an unlikely scenario. If they did decide to exit the market, I'd expect them to do it by spinning off or selling the Optron division because there would still be demand for what they make.

 

If they stopped production entirely then there are quite a few other manufacturers of fluorite around the world, which is one of the advantages of using it over super ED glass - if FPL53 or FCD100 stop being available then switching to a different glass type requires a redesign but fluorite is interchangeable provided the grade is of the necessary quality. There are also numerous companies that make fluorite lenses who could potentially replace Canon Optron as a supplier, although they might be too expensive for the amateur telescope market.

 

If fluorite lenses became too expensive to source then amateur telescopes using it would switch to super ED glass instead. The same is true with any glass type - both Astro-Physics and Takahashi made telescopes that used FPL52, but when Ohara stopped making it those telescopes either had their production stopped or were redesigned to use something else (FPL53 in the case of the Tak TOA-130). Fluorite has been used in optics since the 1880s while glass types come and go.

[azure1961p]

Loads of natural fluorite at the Northeast Gem and Mineral Show. Boxes and boxes!

 

Pete

[RichA]

To those who have poor understanding

Some of you make a HUGE deal out of ou vs. uo as well as d vs. t.
I have the right to do the same, haven't I?

What if Canon do the very same and decide to produce fluoride lenses only furthermore? All those fracs have to be redesigned

https://oharacorp.co...023/08/caf2.pdf

 

Just LOOK at the transmission wavelength range compared to lowly ED glass!

Edited by RichA, 18 October 2024 - 02:28 PM.

[RichA]

Roland Christen, 2012:

"Although readily available, CaF2 is not cheap by any means. A 6" blank of Fluorite from Ohara (Optron) costs approximately $2000. That's about twice as much as FPL-53 ED glass."

[SandyHouTex]

Roland Christen, 2012:

"Although readily available, CaF2 is not cheap by any means. A 6" blank of Fluorite from Ohara (Optron) costs approximately $2000. That's about twice as much as FPL-53 ED glass."

If bought singly, I would agree, but telescope makers would buy in quantity and get a better deal I suspect.