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Comparing FPL-53 and CaF2

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#101 Alan French

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Posted 19 May 2018 - 05:34 PM

A bit about calcium fluoride and its role in lithography.

 

https://onlinelibrar.../opph.201190192

 

Clear skies, Alan



#102 Jon Isaacs

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Posted 19 May 2018 - 05:40 PM

So why do fluorite crystal lenses continue to exist and be used? 

 

It appears to be older technology that is more difficult to work with?

 

What does it provide that newer easier to work with ED glasses do not?  If the answer is nothing, than why is it still around?

One reason is that large FPL-53 blanks are hard to come by... 

 

Jon


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#103 ratnamaravind

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Posted 21 May 2018 - 11:18 PM

Yup- worked for the world’s leading photolithography company ASML (they own a significant portion of Zeiss) for five years with a major R&D facility right here in San Diego. I saw CaF2 everywhere in the labs- beam splitters, mirror windows, etc.



#104 Alan French

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Posted 22 May 2018 - 09:43 AM

I understand FPL53 will not continue to be available.

 

No one has provided any real evidence that FPL55 is "not as good" as FPL53.

 

If look at Vladimir's figure 148 at http://www.telescope...o_refractor.htm you'll see FPL55 not far from FPL53, and some matching glass candidates over on the right.

 

Clear skies, Alan

I wanted to correct this. Apparently FPL53 will still be available, but has a lower melt frequency than the newer FPL55.

 

Clear skies, Alan



#105 Jeff B

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Posted 22 May 2018 - 09:45 AM

As I understand it, one of the difficulties of making FPL-53 is to keep the fluorite used from crystallizing in the glass.  It's a very controlled process with little room for error.  But it's a very precise process for making large CaF2 blanks as well.  

 

If I had to speculate, I'd guess making FPL-53 had reached a plateau in process with a narrow market for the stuff while firms kept getting better at making CaF2 and the market of applications expanded for it.

 

Jeff



#106 Lookitup

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Posted 22 May 2018 - 11:50 PM

Hi Alan, just came in from another Vixen ED115S vs Tak FC100DF Jupiter comparison and reluctantly have to declare the ED with FPL-53 is the clear winner again. Aperture increase shows details easier even compared with CAF2 100mm.  CS Pete



#107 Fomalhaut

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Posted 23 May 2018 - 05:57 AM

... just came in from another Vixen ED115S vs Tak FC100DF Jupiter comparison and reluctantly have to declare the ED with FPL-53 is the clear winner again. Aperture increase shows details easier even compared with CAF2 100mm.

Takahashi still offers the best FPL-53 triplets (TSA and TOA) ever produced.

 

And as for doublets, according to Vla Sacek's tables, FPL53 (together with ZKN7) seems to equal (but not surpass) CaF2 (together with K5). But, as has been shown above, said ZKN7 does not seem to be reliable enough to be coveted the same as Fluorite  -  well, at least in my case.

 

I owned a Vixen Fluorite myself for years and do esteem that brand! However, if going for a doublet today, I think it would still be rather a Tak Fluorite (the optical quality of which is still unsurpassed and the mechanical quality is superior anyway).

 

Oh, you spoke of aperture increase? In this case, I would go for the TSA-120 grin.gif.

Plus a comparison between that one and an ED-115S would be much fairer than between the 115 and a 100...

 

Chris


Edited by Fomalhaut, 23 May 2018 - 07:46 AM.

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#108 Lookitup

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Posted 28 May 2018 - 01:36 AM

roflmao.gif roflmao.gif

Takahashi still offers the best FPL-53 triplets (TSA and TOA) ever produced.

 

And as for doublets, according to Vla Sacek's tables, FPL53 (together with ZKN7) seems to equal (but not surpass) CaF2 (together with K5). But, as has been shown above, said ZKN7 does not seem to be reliable enough to be coveted the same as Fluorite  -  well, at least in my case.

 

I owned a Vixen Fluorite myself for years and do esteem that brand! However, if going for a doublet today, I think it would still be rather a Tak Fluorite (the optical quality of which is still unsurpassed and the mechanical quality is superior anyway).

 

Oh, you spoke of aperture increase? In this case, I would go for the TSA-120 grin.gif.

Plus a comparison between that one and an ED-115S would be much fairer than between the 115 and a 100...

 

 

Takahashi still offers the best FPL-53 triplets (TSA and TOA) ever produced.

 

And as for doublets, according to Vla Sacek's tables, FPL53 (together with ZKN7) seems to equal (but not surpass) CaF2 (together with K5). But, as has been shown above, said ZKN7 does not seem to be reliable enough to be coveted the same as Fluorite  -  well, at least in my case.

 

I owned a Vixen Fluorite myself for years and do esteem that brand! However, if going for a doublet today, I think it would still be rather a Tak Fluorite (the optical quality of which is still unsurpassed and the mechanical quality is superior anyway).

 

Oh, you spoke of aperture increase? In this case, I would go for the TSA-120 grin.gif.

Plus a comparison between that one and an ED-115S would be much fairer than between the 115 and a 100...

 

Chris

Chris, comparison with 4" aperture would be more fair but fluorite would likely win. I'd rather go with a bigger light Tak doublet but no availability. The Vixen ED115S cools fast and is 4 pounds lighter then the Tak 120. Never seen a comparison but a more experienced reviewer https://www.cloudyni...h/#entry1290219 compared it with the TAO130 saw no real difference on Saturn. The Tak fluorite FC100DF reduced FL to 7.4 vs the FPL53 FL 7.7 Vixen with similar color correction and has a more clinical and crisper image. TEC just switched to all Fluorite so either availability of FPL53 is affected or fluorite matches high end scopes better. Maybe still some fluorite magic.  roflmao.gif Cheers Pete

 



#109 SandyHouTex

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Posted 30 May 2018 - 03:33 PM

CaF2 and FPL53 have nearly identical optical properties, however CaF2 offers the advantage of no micro-bubbles.  That's why you can't see a laser trace when shined through it, whereas you can with FPL53.  So it should be better from a scatter standpoint.

 

CaF2 is a little more difficult to work with because it shatters if cooled quickly.  There's the old story that Roland was working with some and a bead of his sweat hit it and it shattered.  But once you have the processes down, it shouldn't be an issue.



#110 gnowellsct

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Posted 30 May 2018 - 04:08 PM

CaF2 and FPL53 have nearly identical optical properties, however CaF2 offers the advantage of no micro-bubbles.  That's why you can't see a laser trace when shined through it, whereas you can with FPL53.  So it should be better from a scatter standpoint.

 

CaF2 is a little more difficult to work with because it shatters if cooled quickly.  There's the old story that Roland was working with some and a bead of his sweat hit it and it shattered.  But once you have the processes down, it shouldn't be an issue.

So now we gonna put 15 years of TEC 140s into the trash bins because they have bad light scatter?



#111 MooEy

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Posted 30 May 2018 - 05:52 PM

I think we are officially on the same level as those audiophile forums.

1. That piece of fluorite is only 1 out of the 6-10 pieces of glass in the entire optical train. The scatter of all the other glasses doesn’t matter?

2. A high power laser is required to see this scatter, how much light do you get from the celestial objects?

3. The green laser will show you scatter not just thru that few CM of FPL-53 glass, it will also show you scatter thru kilometers of atmosphere and probably light years worth of outer space.

Edited by MooEy, 30 May 2018 - 05:52 PM.

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#112 Paul G

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Posted 30 May 2018 - 08:37 PM

I think we are officially on the same level as those audiophile forums.

1. That piece of fluorite is only 1 out of the 6-10 pieces of glass in the entire optical train. The scatter of all the other glasses doesn’t matter?

2. A high power laser is required to see this scatter, how much light do you get from the celestial objects?

3. The green laser will show you scatter not just thru that few CM of FPL-53 glass, it will also show you scatter thru kilometers of atmosphere and probably light years worth of outer space.

Exactly. And Yuri posted in another thread that the difference in scatter isn't visible at the eyepiece.


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#113 gnowellsct

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Posted 30 May 2018 - 09:23 PM

I think we are officially on the same level as those audiophile forums.

1. That piece of fluorite is only 1 out of the 6-10 pieces of glass in the entire optical train. The scatter of all the other glasses doesn’t matter?

2. A high power laser is required to see this scatter, how much light do you get from the celestial objects?

3. The green laser will show you scatter not just thru that few CM of FPL-53 glass, it will also show you scatter thru kilometers of atmosphere and probably light years worth of outer space.

I think you are exactly right, Paul.  And to my consternation I only just today discovered that here on CN we DO IN FACT HAVE an "audiophiliac" forum.   It explains so much.   That's where they train!  :)


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#114 SandyHouTex

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Posted 31 May 2018 - 12:51 PM

So now we gonna put 15 years of TEC 140s into the trash bins because they have bad light scatter?

No, I didn't say that.  All glass optics have micro-bubbles due to cooling.  CaF2, which is a crystalline mineral doesn't.  That doesn't mean you can't make an excellent telescope with FPL-53.  I have two EONs.  An 80mm and a 120mm, both of which use FPL-53.


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#115 SandyHouTex

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Posted 31 May 2018 - 12:55 PM

Exactly. And Yuri posted in another thread that the difference in scatter isn't visible at the eyepiece.

And that, is Yuri's opinion.



#116 SandyHouTex

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Posted 31 May 2018 - 12:57 PM

Exactly. And Yuri posted in another thread that the difference in scatter isn't visible at the eyepiece.

And that, is Yuri's opinion.

 

I think we are officially on the same level as those audiophile forums.

1. That piece of fluorite is only 1 out of the 6-10 pieces of glass in the entire optical train. The scatter of all the other glasses doesn’t matter?

2. A high power laser is required to see this scatter, how much light do you get from the celestial objects?

3. The green laser will show you scatter not just thru that few CM of FPL-53 glass, it will also show you scatter thru kilometers of atmosphere and probably light years worth of outer space.

Okay, so I had an FS-102 and I have an FS-152 which are doublets.  Using the CaF2 has reduced any scatter due to micro-bubbles to half what it would be with a glass.  And I would say I can see a slight difference between my EONs scatter and the FS-152 scatter when I use the same eyepiece.



#117 SandyHouTex

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Posted 31 May 2018 - 01:01 PM

Isn't that why people rave about the ZAO eyepieces, because scatter is reduced with the "Zeiss polish".  If scatter can be reduced with a better polish, why can't it be reduced with a better objective material?


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#118 n2068dd

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Posted 31 May 2018 - 09:15 PM

I think, all of our S-FPL-53 and Fluorite comparison is just only the rumor.

I don't care which is better or not.

Both material is made mainly for vast volume of Canon lens( more than half that Ohara made), They only use as it should used for. In most of TV broadcasting camera, fast zooming lens has vast volume of fluorite elements. If you'd like or dislike for them, both material is still used in many optics. Comparing those of camera lens, telescope volume is very very minor. in a way, most primitive.

In real telescopes, German site had been testing them what really is. You can see at a glans, polishing manner, Strehl ratio, color correction, null image,focus shift and so on. It's enough for me to compare. You can see most of fluorite doublet has color aberration equally as in a S-FPL53 doublet. the site reports many of excellent fluorite triplet could almost fully reduced them, not ED so far. TOA and FOA is the exception. Their optic design method is different than others.

The site, Vladimir Sacek examples are just calculating just by his method. There seems need more to bending process to reduce the spherical aberrations. It's only my opinion.


Edited by n2068dd, 01 June 2018 - 12:26 AM.


#119 MooEy

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Posted 31 May 2018 - 11:16 PM

And that, is Yuri's opinion.

Okay, so I had an FS-102 and I have an FS-152 which are doublets. Using the CaF2 has reduced any scatter due to micro-bubbles to half what it would be with a glass. And I would say I can see a slight difference between my EONs scatter and the FS-152 scatter when I use the same eyepiece.

I’m fairly sure my FPL-53 scopes are way superior. In times of good seeing, I can see the US flag blowing in the wind on the moon.

Edited by MooEy, 31 May 2018 - 11:20 PM.

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#120 gnowellsct

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Posted 31 May 2018 - 11:29 PM

Isn't that why people rave about the ZAO eyepieces, because scatter is reduced with the "Zeiss polish".  If scatter can be reduced with a better polish, why can't it be reduced with a better objective material?

The "Zeiss polish" is the fluid from the user's eye moistening the lens.  It's part of the design.


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#121 Suavi

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Posted 01 June 2018 - 12:44 AM

Just a quick question - is Takahashi using glass or fluorite in its line of refracting astrographs (FSQ) ? And if it is not fluorite, why engineers at Takahashi decided to design fast astrographs with inferior performance for use with unforgiving large CCDs that require excellent off-axis performance?


Edited by Suavi, 01 June 2018 - 04:38 AM.


#122 jeremiah2229

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Posted 01 June 2018 - 12:53 AM

I’m fairly sure my FPL-53 scopes are way superior. In times of good seeing, I can see the US flag blowing in the wind on the moon.

Pfft...the TV-85 here lets me count the stars on that flag and I have no idea what glass is being used.

 

(I couldn't help it)  waytogo.gif

 

 

Peace...


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#123 tonyt

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Posted 01 June 2018 - 01:08 AM

Just a quick question - is Takahashi using glass of fluorite in its line of refracting astrographs (FSQ) ? And if it is not fluorite, why engineers at Takahahashi decided to design fast astrographs with inferior performance for use with unforgiving large CCDs that require excellent off-axis performance?

FSQ owners are not a very picky bunch. Fluorite is so much brighter and more contrasty. grin.gif 

 



#124 n2068dd

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Posted 01 June 2018 - 04:53 AM

Just a quick question - is Takahashi using glass or fluorite in its line of refracting astrographs (FSQ) ? And if it is not fluorite, why engineers at Takahahashi decided to design fast astrographs with inferior performance for use with unforgiving large CCDs that require excellent off-axis performance?

The optic designer at Takahashi only choose the material just for their desired spec. Not material itself. I've heard them how about fluorite possibility, it had been a while FCT-line discontinued. They knew a fluorite still have the advantage than S-FPL53. when used in doublet,he say 10% better. although used in triplet, advantage will be smaller. Not different when FCT was developed, he can select new mating lens and new design method. they can control higher order aberration curve and air lens. FSQ-130 or 106 use 5 or with reducer 6 to 7 lens elements. It's not the telescope, rather camera with highly corrected PSF all over the full 35mm format. When He developed TSA and TOA, he could fulfill the spec as intended. That's it. and He had been saying old FC style still have the interest for him. many possibility. That's why new FC-D  and FOA was released.



#125 MooEy

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Posted 01 June 2018 - 05:43 AM

I'd be honest, as much as I claim that the 2 glass are more or less equal, as per the below link, there are possible mating glass with slightly lower abbe number with similar partial dispersion as fluorite when compared to FPL-53. Whether they are usable or give any improvement, I'm not sure. 

 

http://www.telescope...RPD_diagram.png




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