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Fluorite Refractors

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#51 t.r.

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Posted 01 July 2015 - 07:14 AM

Was wondering what refractors old and new use Fluorite elements in them?

 

I'm quite suprised no one has asked the question...What is the purpose for your inquiry into this and why catalog the results? A forthcoming article perhaps? :hmm:



#52 BillP

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Posted 01 July 2015 - 09:02 AM

 

Was wondering what refractors old and new use Fluorite elements in them?

 

I'm quite suprised no one has asked the question...What is the purpose for your inquiry into this and why catalog the results? A forthcoming article perhaps? :hmm:

 

 

:lol:  No.  No ulterior motive.  Fluorite scopes are always referred to with such mystique, was just curious how many there actually are and were that use them.  Nice to have a good list to in case I get an itch to pick up one used.  Don't have any fluorite in the stall and maybe I should given all the mystique about them.



#53 Starhawk

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Posted 01 July 2015 - 09:13 AM

There isn't a major advantage in CaF2 over FPL-53. Several authors on this thread appear to be confusing FPL-53 with FPL-51.  The main reason to go with CaF2 these days is to avoid competing with furnace runs dedicated to smartphone camera glass. 

 

FPL-53 and other optical glasses:

http://www.oharacorp...-chart-2015.pdf

 

CaF2 properties:

http://refractiveind...ok=CaF2&page=Li

 

-Rich


Edited by Starhawk, 02 July 2015 - 08:24 AM.

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#54 Jeff B

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Posted 01 July 2015 - 09:26 AM

 

Someone mentioned that with FPL-53 there could be small variations in the properties that, for best results, would require characterization of each melt, something Astro-Physics does. In the same way, I would think the mating elements would require characterization as they are also glasses and subject to small variations.

 

Jon

 

 

So true.  During a recent progress update, Yuri mentioned that the first two lenses for the 250FL did not completely live up to expectations due to variations in one of the mating elements, not the fluorite.

 

Jeff



#55 GJJim

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Posted 01 July 2015 - 09:47 AM

I also have to comment concerning the "laser" test.  I do see a difference in "scatter" in some of the comparison photos I've seen but I have to ask, does it really matter?  I mean a laser is just an incredibly intense light source.  What I see in the photos is a very mild side/back scatter that my gut tells me is vanishingly small compared the axial intensity of the beam.   So is there, in the real world, a  real practical advantage (like being actually visible in the eyepiece or even a CCD sensor) in "scatter" of CaF2 compared to optical glass?   

No advantage at all since, as you point out, starlight is far less intense than the laser. It's just a simple means to determine what material is actually in the objective. With fluoro-crown glasses there is no way for an end user to know which type of glass was used to make their lens. A recent thread mentioned a Chinese scope marketed by various resellers all claiming a different glass combination in the objective.



#56 macdonjh

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Posted 01 July 2015 - 09:56 AM

There isn't a major advantage in CaF over FPL-53. Several authors on this thread appear to be confusing FPL-53 with FPL-51.  The main reason to go with CaF2 these days is to avoid competing with furnace runs dedicated to smartphone camera glass. 

 

FPL-53 and other optical glasses:

http://www.oharacorp...-chart-2015.pdf

 

CaF2 properties:

http://refractiveind...ok=CaF2&page=Li

 

-Rich

 

Oh yes there is.  Fluorite is magic and FPL-53 is science.  Didn't you read the early posts?

 

I have to admit that the view through a friend's Tak FS-102 had a certain magic that I remember several years later.  This from an observer that has such a case of aperture fever (aperture snobbery?) that I don't use 4" scopes anymore.


Edited by macdonjh, 01 July 2015 - 09:57 AM.

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#57 mark8888

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Posted 01 July 2015 - 10:03 AM

For whatever its worth, my experience has been that I have seen significantly more scatter with a TEC 140 compared to a TEC 180. Specifically I'm talking about the area immediately around Saturn. Is that due to the fluorite in the 180, the extra aperture, variation in scopes, some other factor?  I have no idea.  And I didnt have them side by side at the same time, and the EPs I used may have been different!  So yes it could have been caused by a lot of factors.  But anyway I thought I'd mention it. 


Edited by mark8888, 01 July 2015 - 10:07 AM.


#58 Erik Bakker

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Posted 01 July 2015 - 12:14 PM

Fluorite in well executed good designs gives incomparably pure views. Any f/8, or better yet f/9 fluorite doublet in 55mm-102mm gibes outstanding images after very little cool down time. Eyepieces like medium to slowish f/ratios too, especially 4-5 element classic designs like ethos or Brandons. In the 125-152mm apertures you enter a zone where the incredible contrast and freedom from scatter have to compete with the increasing chromatic aberration. Here we would ideally want to see f/10 - f/12 instruments. But these are just too big for most of us

 

Now if you consider a fluorite doublet with a mating element that brings out the best in combination with a fluorite element, performance improves even further. But that makes it less suitable for larger volume production runs. 


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#59 Markab

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Posted 01 July 2015 - 01:04 PM

 

 

 

And that's a problem, because the difference between the high end an the cheap stuff is so small. ;)

 

 

It certainly can be; you generally pay dearly for the last 20% of performance at the eyepiece or the sensor.  But you would be surprised how good some inexpensive imported telescopes are and how poor some high-end samples can be.

 

 

Indeed. That is probably why we are seeing deflating prices for AP scopes while vendors such as Expl@re Scientific are looked upon increasingly favorably...because the quality differential at the eyepiece [not workmanship and build quality where high end scopes are vastly superior and so is quality control] is becoming increasingly small.



#60 Derek Wong

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Posted 01 July 2015 - 03:27 PM

I guess Markus wants to make a statement - 

 

http://www.astromart...ified_id=890530

 

includes 304mm fluorite f/8 refractor

 

This is a signature product, but I think I would customize it to a 14" doublet fluorite and 6" white light and H-alpha scopes with a nice rotating massage chair.

 

Derek



#61 Element79

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Posted 01 July 2015 - 03:53 PM

Wow!  Only one million bucks!  I think that I need two of them to make binoscopes...



#62 Jayo

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Posted 02 July 2015 - 03:03 AM

Fluorite obviously has advantages over Super ED glass. Especially for fast systems.

Nikon today... introduced two new telephotos(500 & 600) incorporating the very expensive fluorite element (previous models only had Super ED). Canon already uses fluorite.

 

''...incorporated fluorite lens elements to reduce weight, minimize aberrations and improve overall image quality.''

 

http://www.bhphotovi...es-ReadMoreBttn


Edited by Jayo, 02 July 2015 - 03:14 AM.


#63 Jon Isaacs

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Posted 02 July 2015 - 03:27 AM

Fluorite obviously has advantages over Super ED glass. Especially for fast systems.

Nikon today... introduced two new telephotos(500 & 600) incorporating the very expensive fluorite element (previous models only had Super ED). Canon already uses fluorite.

 

''...incorporated fluorite lens elements to reduce weight, minimize aberrations and improve overall image quality.''

 

http://www.bhphotovi...es-ReadMoreBttn

 

I saw nothing that explained those "obvious" advantages over FPL-53.  Just what are those "obvious" advantages?

 

Jon


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#64 cjc

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Posted 02 July 2015 - 08:27 AM

 

Fluorite obviously has advantages over Super ED glass. Especially for fast systems.

Nikon today... introduced two new telephotos(500 & 600) incorporating the very expensive fluorite element (previous models only had Super ED). Canon already uses fluorite.

 

''...incorporated fluorite lens elements to reduce weight, minimize aberrations and improve overall image quality.''

 

http://www.bhphotovi...es-ReadMoreBttn

 

I saw nothing that explained those "obvious" advantages over FPL-53.  Just what are those "obvious" advantages?

 

Jon

 

Marketing, for one...


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#65 Starhawk

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Posted 02 July 2015 - 08:35 AM

You are mistaken- there just isn't the difference you claim. The biggest problem recently is FPL-53 is too good for its major commercial application to be available for small niche applications like telescopes or ultra-high end camera lenses. Check out your own FSQ-106ED- it doesn't suffer from using FPL-53 instead of Calcium Fluoride.

 

Calcium Fluoride was never picked up for mass manufacturing thanks to serious yield problems it presents, so it has continued to be available while smart device cameras have cornered the FPL-53 supply. 

 

Your ad copy isn't comparing to FPL-53- it's referring to common achromatic lenses. 

 

The return to CaF2 isn't good news for us. It means APO scopes will be much more expensive, and likely signals the end of the golden age of APOs. 

 

-Rich

 

Fluorite obviously has advantages over Super ED glass. Especially for fast systems.

Nikon today... introduced two new telephotos(500 & 600) incorporating the very expensive fluorite element (previous models only had Super ED). Canon already uses fluorite.

 

''...incorporated fluorite lens elements to reduce weight, minimize aberrations and improve overall image quality.''

 

http://www.bhphotovi...es-ReadMoreBttn


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#66 BillP

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Posted 02 July 2015 - 09:27 AM

The return to CaF2 isn't good news for us. It means APO scopes will be much more expensive, and likely signals the end of the golden age of APOs. 

 

Did I miss yet another golden age :confused:


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#67 vahe

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Posted 02 July 2015 - 09:27 AM

I sometimes wonder how the skeptics would reconsider their opinions on fluorite advantage if Roland had chosen to use fluorite instead of FPL-53 for his larger refractors.

Is it a coincidence that AP’s faster and more desirable Stowaway is fluorite and not FPL53?

Vahe
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#68 JJK

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Posted 02 July 2015 - 11:26 AM

 

 

 

 

And that's a problem, because the difference between the high end an the cheap stuff is so small. ;)

 

 

It certainly can be; you generally pay dearly for the last 20% of performance at the eyepiece or the sensor.  But you would be surprised how good some inexpensive imported telescopes are and how poor some high-end samples can be.

 

 

Indeed. That is probably why we are seeing deflating prices for AP scopes while vendors such as Expl@re Scientific are looked upon increasingly favorably...because the quality differential at the eyepiece [not workmanship and build quality where high end scopes are vastly superior and so is quality control] is becoming increasingly small.

 

 

A friend of mine, who went through two ES scopes, would suggest otherwise.


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#69 BillP

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Posted 02 July 2015 - 08:23 PM

 

 

Indeed. That is probably why we are seeing deflating prices for AP scopes while vendors such as Expl@re Scientific are looked upon increasingly favorably...because the quality differential at the eyepiece [not workmanship and build quality where high end scopes are vastly superior and so is quality control] is becoming increasingly small.

 

 

A friend of mine, who went through two ES scopes, would suggest otherwise.

 

 

A sample of 2 from a very large population is statistically and scientifically meaningless.

 

We've seen in these forums pics of flocking coming off inside TV scopes, oil leaks from TEC140s, oil cavitation and fungus on AP scopes.  So all brands have issues, does not make any one brand poor because of it.  Stuff happens.


Edited by BillP, 02 July 2015 - 08:52 PM.

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#70 JJK

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Posted 03 July 2015 - 09:45 AM

 

 

 

Indeed. That is probably why we are seeing deflating prices for AP scopes while vendors such as Expl@re Scientific are looked upon increasingly favorably...because the quality differential at the eyepiece [not workmanship and build quality where high end scopes are vastly superior and so is quality control] is becoming increasingly small.

 

 

A friend of mine, who went through two ES scopes, would suggest otherwise.

 

 

A sample of 2 from a very large population is statistically and scientifically meaningless.

 

We've seen in these forums pics of flocking coming off inside TV scopes, oil leaks from TEC140s, oil cavitation and fungus on AP scopes.  So all brands have issues, does not make any one brand poor because of it.  Stuff happens.

 

Think whatever you want.

 

My comment wasn't based on subjective info.   From I what I observed, I personally wouldn't bother with ES for imaging.  These scopes certainly have their place, but I would prefer to have better optics (an objective that can handle blue light better) and better machined parts.

 

Fungus on an objective is hardly a manufacturer's issue.   What I saw firsthand on the two ES scopes was not due to a fluctuation.  The objective's performance is integral to its design (it did fine with red and green filters, but not blue), and the slop in the focuser is not acceptable to me (I feel the same way about those on a lot of Taks I've seen).  For visual work, the scopes would probably be ok (I'd still prefer a better scope and I can afford them).


Edited by JJK, 03 July 2015 - 09:51 AM.

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#71 Derek Wong

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Posted 03 July 2015 - 11:22 AM

Fluorite obviously has advantages over Super ED glass. Especially for fast systems.

Nikon today... introduced two new telephotos(500 & 600) incorporating the very expensive fluorite element (previous models only had Super ED). Canon already uses fluorite.

 

''...incorporated fluorite lens elements to reduce weight, minimize aberrations and improve overall image quality.''

 

http://www.bhphotovi...es-ReadMoreBttn

 

This has little to do with the discussion in telescopes.  The Nikon 600mm had 10 elements with 3 ED elements (the site lists them as ED, not super ED whatever that means).  The new lens is lighter but has 16 elements, with 2 fluorite and 4 ED elements.  Zoom camera lenses have to be sharp over the entire focal range, not just at infinity with wider correction.  This requires solving a multidimensional problem, and having fluorite and ED elements gives more choices and therefore a better solution than just using ED (or just using fluorite) because the two types will behave differently.  Canon does the same, using fluorite and ULD elements.  There is a large marketing aspect of this as well, with Nikon all of a sudden touting fluorite after years of just using ED and super ED.

 

Derek


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#72 BillP

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Posted 03 July 2015 - 11:47 AM

 

Think whatever you want. ... Fungus on an objective is hardly a manufacturer's issue.  

 

 

Well, it is not thinking whatever, it is established statistical science.  You can't draw any conclusion from a sample of 2 when the population is large.   Even if only 100 scopes were made, if you want to have a confidence level of 90% in your results and you can accept a 10% margin of error, your sample size needs to be 41, not 2.  With a sample of 2 your margin of error is 80%!

 

And not entirely true on the fungus issue.  When any organics are used in the scope, or in the carry case, then you are inviting fungus growth as spores can be in those items...and when airborne spores come in contact with that it gives them a place to settle down and start a colony.  So any wood materials in the case, any petroleum based lubricants on mechanicals, any cork or similar products used to cushion the objective, etc.  Some manufacturers have done this, including top tier premiums. 


Edited by BillP, 03 July 2015 - 11:58 AM.

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#73 BillP

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Posted 03 July 2015 - 12:15 PM

 

I have never heard of an AP scope coming from Astro-Physics with fungus on it - never, ever.  I have never heard of an AP scope coming from Astro-Physics with fungus on it - never, ever. Nor have I ever heard of a TeleVue scope coming from TeleVue with the flocking peeling off. Nor have I ever heard of a TEC140 coming from TEC with oil leaking out of it.

 

I never said fungus out the door so think you are incorrectly reading what I wrote.  It would be silly to think this.  However, have certainly seen people trying to sell fungus ridden optics online!  Issues happen immediately, and others over time.  They are many times though in the end original design/engineering issues.

 

On the peeling off flocking and TEC oil leaks they are all from members at CN and in the archives.  SteveC was one of the oil leaks.  Teelgul was one of the people with flocking falling off.  And of course, when you haunt other forums you see that these things happen now and again.  So one needs to examine the engineering of any scope and evaluate what may be longevity issues and then decide if it can be an issue for them.  On the AP scopes, I love that they mill the baffles...a really nice move.


Edited by BillP, 03 July 2015 - 12:24 PM.

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#74 roadi

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Posted 03 July 2015 - 12:59 PM

 


 

As an aside, I'll agree with JJK on TAK mechanics as well. All three of the scopes I owned FS-60, Sky-90, FSQ-105 had crappy wobbly sloppy focusers. The Sky-90 II had the cold weather pinched optic problem which Takahashi to its credit replaced with an entirely new telescope NSV model. Of the three scopes, the 60mm finder/guider and the FSQ have been sold. The Sky90II NSV is now my son's, but the second thing I did to it, was replace the first thing I did to it, which was the add-on garbage micro-whatever-it-was-called, with a Starlight FT pinion.

 

Did you buy all four taks new? quite a harsh statement on the focusers you have on your taks! If bought second hand the crappy focuser thing might be related to someone else rather than the manufacture!!

I've had four Tak refractors too, one still and none had focuser issues. Not a feathertouch class focuser but definately excellent. :)


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#75 JJK

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Posted 03 July 2015 - 01:08 PM

 

 

Think whatever you want. ... Fungus on an objective is hardly a manufacturer's issue.  

 

 

Well, it is not thinking whatever, it is established statistical science.  You can't draw any conclusion from a sample of 2 when the population is large.   Even if only 100 scopes were made, if you want to have a confidence level of 90% in your results and you can accept a 10% margin of error, your sample size needs to be 41, not 2.  With a sample of 2 your margin of error is 80%!

 

And not entirely true on the fungus issue.  When any organics are used in the scope, or in the carry case, then you are inviting fungus growth as spores can be in those items...and when airborne spores come in contact with that it gives them a place to settle down and start a colony.  So any wood materials in the case, any petroleum based lubricants on mechanicals, any cork or similar products used to cushion the objective, etc.  Some manufacturers have done this, including top tier premiums. 

 

I know more than a bit about statistics, machining, optics, and inference.

 

The mechanicals on the ES can't perform well enough to suit my needs.  The design simply doesn't allow it.  In addition to the two I saw up close more than casually, I saw the scopes at ASAE and NEAF.  Nothing I saw at those events suggested I should change my opinion.

 

For imaging, how well do you think the ES scopes should perform in the blue, compared to an AP155 EDF?

 

i'm not knocking the scopes.  They do quite well for their cost, and might be very good for visual work.  I wouldn't want to spend my time looking for a statistical outlier for imaging.

 

Your fungus argument just became even more stretched.


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