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Fluorite EP's

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#26 Jon Isaacs

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Posted 11 September 2015 - 09:21 AM

If everything in the universe were done to be practical/advantageous, then indeed it would be a dull and lackluster place IMO.  There is a fascination for many with the Fluorite crystal.  The very fact that it is a single crystal is intriguing for many...and therefore it becomes advantageous!  I would want to have one...just because...which is plenty sufficient reason in itself, and at times this is more of a reason to do it than anything "practical".  :grin:

 

 This is the eyepiece forum and the technical aspects of the eyepiece are important. One could desire a diamond encrusted barrel with gold inlay but that's a personal issue and one would not expect manufacturers to support that market as there is no optical reason for doing so. 

 

In the case of using Fluorite, I think it's very reasonable to ask the question whether the properties of Fluorite make it a good choice for eyepieces and Barlows. It maybe that the inclusion of Fluorite in an eyepiece would be a real disadvantage and result in an eyepiece that was a poor performer when compared to an eyepiece manufactured with more normal glasses. That is a question someone like Ernest can answer.

 

You may want an eyepiece made with Fluorite just to have one. I am indeed a practical man, I buy my eyepieces to view the wonders of the heavens above, those views are far from dull and lackluster. Indeed each moment is very special and magical...  I guess I can be thankful that the thought of a Fluorite eyepiece is not necessary to provide spice and excitement to my time under the night sky.. 

 

if an eyepiece with Fluorite element(s) did offer an optical advantage, that would make it of interest to me.. 

 

jon


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#27 BillP

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Posted 11 September 2015 - 09:31 AM

 

This is the eyepiece forum and the technical aspects of the eyepiece are important. One could desire a diamond encrusted barrel with gold inlay but that's a personal issue and one would not expect manufacturers to support that market as there is no optical reason for doing so. 

 

It is fine to be "practical", but this does not mean every needs be nor that practical is the end-all measure of something.  Aesthetics are important and we all know this when eyepieces are marketed that look "funny" or "ugly".  So you certainly cannot ignore aesthetics at all, not if you want a successful product.  And then there was a time when people were enthralled with Lanthanum as well, but as we see today, there is no practical "need" for it as TV has designed it out of their new wares very successfully.  Manufactures need to support the market's consumers, period, regardless if that support it practical, advantageous, superfluous, aesthetic, desirous, etc.  So if all they support is what is optically relevant, then in the end they will not be meeting the needs of the customers. 


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#28 Eddgie

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Posted 11 September 2015 - 09:36 AM

Jon,

 

Reason cannot be used to conquer a post in the refractor forum.  If it is written, it must be true.

 

Fluorite is better.  I read it in the refractor forum.  It has less scatter, less absorption, and cools faster.

 

ED Scopes can't be as good as Fluorite scopes.   As it turns out, the perfect refractor can't really be perfect unless it has Fluorite lenses, and now it would appear that neither can your barlow or eyepeice

 

My answers may seem to be quite sarcastic, but I feel as if CN has reached a new level of extraneous debate with claims that are so fantastic that logic is dead.  

 

Any anyone that is so convinced that Fluorite is so much better should start their own line of Fluorite Barlows.   I am sure the world will beat a path to their web site.

 

Un-winnable Jon.   Why try?  Guy want's a Fluorite Barlow..   Let him get one.   It will be better.  I promise it will.   When I read reviews for all of this stuff, the buyer that has spend a lot of money on it always reports a great increase in performance. 

 

It will be that way here to...

So some people will want Fluorite refractors, Fluorite Barlow, Fluorite Eyepeices, and even oh my gosh, Fluorite Diagonals!



#29 Starman1

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Posted 11 September 2015 - 09:49 AM

 

 

Bar and Zeiss make fluorite barlows - I suppose the APm could be a rebadged Zeiss. I recall the Baaders are rebadged Zeiss, customised with the Baader locking system.

 

There is also a barlow/extender made for Astrophysics. Again, Zeiss I by memory (or rebadged to Baader), and all fluorite.

 

BUT, I need a CaF2 EP for the FSQ-106N (2 x fluorite elements)

 

Why do you need a Fluorite Barlow? 

 

Jon

 

 

Less scatter and faster cooling.

 

Or so I have read.   LOL...

 

And yet another strike against everything but refractors. SCTs and MCTs will never have fluorite correctors so will never scatter less and cool faster.

But that is OK.  I like it when the SCTs stay together.  When they scatter, it is hard to round them up.   

 

A good cutting horse helps.

 

Barlows, being very small, probably can't get that far out of site that a good cutting horse would be necessary..    But cooling faster means you can't use your thermal imaging camera to find them hiding under leaves.

 

Oh..  Not that kind of Scatter?   Never mind....

 

Though your post was tongue-in-cheek I believe, I investigated and found that CaF2 has a specific heat and refractive index very similar to many glass types.

so reduction in scatter would be solely due to polishing and adherence to the optical design.

The specific heat is nearly identical to glass, so cooling would be about the same rate as well.

There is a problem with applying the best broadband anti-reflection coatings as well, but that could possibly be due to a lack of research in appropriate materials for coating.

I could find no particular reason why a manufacturer would even use the material, given its other physical constants, other than for purposes of marketing.

Glasses of a wide variety of refractive indices are available today that weren't available 30-40 years ago.  Unless there is a particular reason to go back to long focal ratio doublets in refractors, or because CaF2 is more available than glass types needed, it is a mystery why CaF2 is being used.


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#30 Scott in NC

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Posted 11 September 2015 - 10:01 AM

So some people will want Fluorite refractors, Fluorite Barlow, Fluorite Eyepeices, and even oh my gosh, Fluorite Diagonals!

 

Hmm...I wonder if a prism can be (or even should be :shrug:) made of fluorite.  I wonder how well that would refract light in the proper manner?



#31 Jon Isaacs

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Posted 11 September 2015 - 10:18 AM

 

 

This is the eyepiece forum and the technical aspects of the eyepiece are important. One could desire a diamond encrusted barrel with gold inlay but that's a personal issue and one would not expect manufacturers to support that market as there is no optical reason for doing so. 

 

It is fine to be "practical", but this does not mean every needs be nor that practical is the end-all measure of something.  Aesthetics are important and we all know this when eyepieces are marketed that look "funny" or "ugly".  So you certainly cannot ignore aesthetics at all, not if you want a successful product.  And then there was a time when people were enthralled with Lanthanum as well, but as we see today, there is no practical "need" for it as TV has designed it out of their new wares very successfully.  Manufactures need to support the market's consumers, period, regardless if that support it practical, advantageous, superfluous, aesthetic, desirous, etc.  So if all they support is what is optically relevant, then in the end they will not be meeting the needs of the customers. 

 

 

Bill:

 

Aesthetics can be important, an ugly eyepiece, it may be a poor seller.

 

But one cannot ignore the optical design and the material properties of the glasses. Again,I ask the simple question:

 

Do the optical properties of Fluorite provide any advantage in the design of eyepieces?  

 

Is there any optical reason to choose Fluorite for any of the elements in an eyepiece?

 

People were enthralled with Lanthanum glasses for eyepieces because their high indexes did provide designers with some real advantages.. That was not an aesthetic issue but an optical issue.

 

Would you purchase an eyepiece with Fluorite elements knowing that the Fluorite detracted from its optical performance?  Would you expect manufacturers to produce eyepieces with Fluorite elements knowing that the Fluorite detracted from performance?

 

My question is a simple one and clearly relevant to the use of Fluorite in eyepieces..  

 

Jon



#32 jeffmac

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Posted 11 September 2015 - 11:12 AM

The last scope i saw with a calcium fluorite element was a 4" Celestron (made by Vixen) in the '80s.

It was ridiculously expensive for the time.

I just saw some lab tests on the objective lenses and, uh, they weren't very good.

Colorless, but not even 1/4 wave on the wavefront.

 

 

Don, I have to believe this was an aberration and not the norm. The 102F lenses from Celestron were (are) held in high esteem. To quote someone, Roland Christen IIRC, referring to that lens: "that was a honey of a lens". I have a C102F, and while it is not perfect, I have seen detail in the GRS on Jupiter with it. It rivals my Tak FC100, although the star test is a little better in the Tak. IIRC, there were reports of some "lemon" C102F's floating around some years ago, but any optical deficiency I don't believe was due to the use of fluorite.

 

Jeff


Edited by jeffmac, 11 September 2015 - 06:30 PM.


#33 Scott99

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Posted 11 September 2015 - 11:40 AM

the refractor forum - some of us insist on Fluorite lenses, some just don't like scopes made of plywood and wingnuts.  I guess everyone has different priorities

 

in a more serious vein - why do they make lenses with FL?  I assume it's because, for a given aperture, FL combined with whatever suitable mating element is available will yield the best color correction.   In certain sizes and f/ratios you can't obtain the right combination of FPL53 and mating elements with available glasses. 

 

From reading the manufacturers' postings it sounds like it's very difficult to obtain FPL53 in larger sizes at the right quality level.  And often the mating elements for FPL53 and/or FL aren't available and they're forced to postpone the run or change designs.


Edited by Scott99, 11 September 2015 - 11:42 AM.


#34 Saturninus

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Posted 11 September 2015 - 11:51 AM

I've always wondered why fluorite is always touted in binoculars and such, but never in EPs. In EPs, it is always lanathum this lanathum that. But they again, I'm not an optical engineer, so I just assume they know what they are doing and I do not and that's fine.

#35 dotnet

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Posted 11 September 2015 - 12:46 PM

Doesn't fluorite (calcium fluoride), um, fluoresce? Could that be the reason Tak FS* owners complain about light pollution more often than others?  :lol:


Edited by dotnet, 11 September 2015 - 12:48 PM.

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#36 Tom T

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Posted 11 September 2015 - 01:54 PM

Those seriously curious about optical design  may want to check out OSLO-Edu.

 

http://www.lambdares.com/oslo

 

FWIW, FPL-53 and OK4 are often considered synthetic fluorite or fluorite glass.  (I believe I recall Roland Christen using the term in days past.)  FPL-53 contains fluorite and is purportedly much easier to work with while providing very similar optical properties.

 

For amateur astronomers, I'm not sure there's really much (if any) advantage to CaF2 any more (except perhaps advertising).  

 

However, it's been said that "The heart wants what it wants".  So - hey.


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#37 Jon Isaacs

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Posted 11 September 2015 - 02:08 PM

 

in a more serious vein - why do they make lenses with FL?  I assume it's because, for a given aperture, FL combined with whatever suitable mating element is available will yield the best color correction.   In certain sizes and f/ratios you can't obtain the right combination of FPL53 and mating elements with available glasses.

 

If you look at FPL-53 Fluorite in relation to the Abbe normal line, there's not much difference.. 

 

Jon


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#38 Jon Isaacs

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Posted 11 September 2015 - 02:12 PM

I've always wondered why fluorite is always touted in binoculars and such, but never in EPs. In EPs, it is always lanathum this lanathum that. But they again, I'm not an optical engineer, so I just assume they know what they are doing and I do not and that's fine.

 

Binoculars can exhibit chromatic aberration due to the fast objectives.  ED glasses can provide better color correction.... 

 

Lanthanum glasses have a high index of refraction which, for whatever reason, is advantageous in eyepiece design.. 

 

Jon



#39 hottr6

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Posted 11 September 2015 - 02:19 PM

Reason cannot be used to conquer a post in the refractor forum.  If it is written, it must be true.

 

Fluorite is better.  I read it in the refractor forum.  It has less scatter, less absorption, and cools faster.

 

ED Scopes can't be as good as Fluorite scopes.   As it turns out, the perfect refractor can't really be perfect unless it has Fluorite lenses, and now it would appear that neither can your barlow or eyepeice

:funny:   :rofl:

 

Don't worry, the reflector and CAT guys/gals have their own dogmas.



#40 BillP

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Posted 11 September 2015 - 02:42 PM

Aesthetics can be important, an ugly eyepiece, it may be a poor seller.

 

But one cannot ignore the optical design and the material properties of the glasses. Again,I ask the simple question:

 

Do the optical properties of Fluorite provide any advantage in the design of eyepieces?  

 

 

Well it's fine for you to ask it, especially if it is meaningful for you.  But realize that it may not be meaningful to others and that your characterization of meaningfulness does not trump other people's characterization of meaningfulness.  In this thread, we have an OP who is a addict for Fluorite.  So we know the reasons for the desire.  What does it matter if optically more advantageous or not?  No, it does not matter in the context of this thread!  So might be fine for another thread, but in this one the OP desires a Fluorite EP and is asking others if they know of any.  But as usual, the practical/meaningful/optical police are gathering trying to change the direction of the thread into where their herd want to take it. :lol:   I prefer to just revel in the OPs addition to wanting Fluorite everything.  It is a fun optical material that has a following and a mystique and some industry experts, like Takahashi, feel it has a special advantage (and they are not armchair quarterbacks). 

 

So...GO FLUORITE!!  Every telescope should have something with Fluorite on it, finder, EP, Barlow!  Otherwise, it is just a plain vanilla telescope :lol:   If all my telescopes had were practical things, they would be IMO as interesting as door knobs. :lol:


Edited by BillP, 11 September 2015 - 02:45 PM.


#41 BillP

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Posted 11 September 2015 - 02:46 PM

However, it's been said that "The heart wants what it wants".  So - hey.

 

 

Put another way...

 

42!



#42 Jeff B

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Posted 11 September 2015 - 03:00 PM

Why use fluorite when you can make a really good eyepiece out of plastic?   :grin:

 

http://www.cloudynig...e-23m-aspheric/

 

 

Jeff



#43 Starman1

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Posted 11 September 2015 - 04:12 PM

 

However, it's been said that "The heart wants what it wants".  So - hey.

 

 

Put another way...

 

42!

 

Actually, it's "37" (see pix of NGC2169:  https://upload.wikim...px-NGC_2169.jpg  ) :lol:


Edited by Starman1, 11 September 2015 - 04:13 PM.

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#44 Larry Geary

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Posted 11 September 2015 - 05:13 PM

 

I prefer to just revel in the OPs [addiction] to wanting Fluorite everything.

 

I hope he goes all the way and gets fluorite eyeglasses or contact lenses.



#45 range88

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Posted 11 September 2015 - 06:46 PM

Fluorite is actually very similar to fpl53 in optical property. But 53 is superior in regards to physical characteristics.
The reason some large apos use fluorite instead of 53, as far as I know, is they are just unable to get 53 glass that large though OK4 can be made to very large slabs. The result is LZOS can make very large apos up to 510mm, while no other consumer optic producer can.

#46 LewisM

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Posted 11 September 2015 - 07:01 PM

He went thataway...no thataway... this thread is not made out of fluorite - it has scattered everywhere!!!

 

Fluorite prism diagonal... now we are talking! And eyeglasses - yes please!! Maybe even my dining table glassware.

 

SCT's with fluorite corrector? Heck, that might mean an SCT might finally get a decent image! Lord knows both Meade and Celestron would benefit from it.



#47 csrlice12

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Posted 11 September 2015 - 07:22 PM

Would you clean them with a toothbrush????



#48 Jon Isaacs

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Posted 11 September 2015 - 10:15 PM

 

Well it's fine for you to ask it, especially if it is meaningful for you.  But realize that it may not be meaningful to others and that your characterization of meaningfulness does not trump other people's characterization of meaningfulness.  In this thread, we have an OP who is a addict for Fluorite.  So we know the reasons for the desire.  What does it matter if optically more advantageous or not?  No, it does not matter in the context of this thread!

 

Bill:

 

I have not seen an answer to my questions from LewisM, you have expressed your opinions and interpretations but so far Lewis has not responded.   Personally I do not view Lewis as a addict for Fluorite, that's your judgment.  I see him as someone who appreciates excellent optics and has had good experiences with Fluorite telescopes and has a somewhat skewed view of the value of Fluorite but I think he is open to reason.. 

 

Do you really think that asking whether Fluorite is a reasonable material for eyepieces is only meaningful to me?  Would you really spend the money on a Fluorite eyepiece if it was a poor performer when compared an ordinary eyepiece?

 

Jon

 

 



#49 BillP

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Posted 11 September 2015 - 10:42 PM

Yes ... I have lots of less than stellar performing eyepieces because they have other attributes that make them special.  If I was after cold clinical lifeless views then I use the sterile designs, if I want more personality then I use the "poor performers" :grin:   And I would LOVE to have an eyepiece with Fluorite regardless if it were not someone else's idea of good.  Just he way it is.  I don't pay homage to math and formulas as I prefer heart.


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#50 Jon Isaacs

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Posted 11 September 2015 - 11:30 PM

Yes ... I have lots of less than stellar performing eyepieces because they have other attributes that make them special.  If I was after cold clinical lifeless views then I use the sterile designs, if I want more personality then I use the "poor performers" :grin:   And I would LOVE to have an eyepiece with Fluorite regardless if it were not someone else's idea of good.  Just he way it is.  I don't pay homage to math and formulas as I prefer heart.

 

Designers and manufacturers have to pay homage to math, material properties and models, eyepieces just don't happen.  I don't think Supermonos just happened or Ethos eyepieces just happened..  Abbe orthos didn't just happen.. Someone had to design them based on optics and material properties.. 

 

If Fluorite could be used to an advantage in an eyepiece, it is entirely possible, such an eyepiece would be the result of the designers understanding of the material properties, formulas and math.  And only a crappy eyepiece Fluorite were possible, it would still be the result of the designers understanding of the material properties, formulas, optics and math.. 

 

As an eyepiece aficionado, you have absolutely no interest in knowing whether Fluorite has any possible advantages in an eyepiece?  That does not interest you?  That's the question I am asking.

 

:shrug:

 

Jon


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