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Yuri May Move to Fluorite for the Tec 140

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#1 Kent10

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Posted 15 June 2017 - 11:26 AM

Yuri has said that Ohara is moving from FPL53 in favor of FPL55, so they are thinking about the future of their APO140.  They still  have about 30 sets of optics for the FPL53 version, but that will end soon.
After that production of APO140 will be postponed for a short time so they can switch to a different glass combination.

 

They may move to Fluorite for the 140 because it “has more margin of safety.”

 

I hope I am understanding this all correctly but I find it very interesting. 

 

https://groups.io/g/...s/message/27694


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#2 RAKing

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Posted 15 June 2017 - 11:50 AM

Interesting, thanks for sharing.

 

This probably won't affect me because I plan to keep my current TEC 140 as long as I can -- plus I doubt if my eyes could tell the difference. lol.gif 

 

Cheers,

 

Ron


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#3 Scott99

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Posted 15 June 2017 - 12:45 PM

there may not be any visible difference, if you look at the spherochromatism numbers Yuri posted recently, the current run of the 140's was improved and is barely different from TEC's FL lineup:

 

>>the current current run of APO140s is a bit different comparing to original design 2002, it is better corrected for blue end part of spectrum:

WL† Cat. design (2002) IX run design (2015)

438nm 0.29 0.75
486nm 0.92  0.95
546nm 0.99  0.99
656nm 0.85  0.87

 

WL 160FL 2014

436nm 0.66
486nm 0.87
546nm 0.99
656nm 0.92

 

  (180 f/7)

436 - 0.46
486 - 0.89
546 - 0.99
656 - 0.93



#4 Kent10

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Posted 15 June 2017 - 01:22 PM

I believe Yuri has been asked before why or if he would ever use Fluorite in the 140 and the reason he did not was because it would cost more.  How many would pay the extra?  But now if FPL53 is hard to get he may be required to use Fluorite or go to a "lesser" glass such as FPL55.



#5 MGD

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Posted 15 June 2017 - 04:42 PM

Isn't it a bit of a stretch to refer to FPL55 as a "lesser glass? Correct me if I'm wrong but isn't that what CFF uses in their larger scopes? Another question aren't fpl53 and FPL55 almost the same and in this context to be fair they are both lesser when compared to fluorite? Just a few things to ponder but I wouldn't consider a FPL55 based TEC 140 as a lesser instrument than the current version.



#6 astrophile

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Posted 15 June 2017 - 04:52 PM

I was told by one high-end apo maker that FPL55 could result in just as good or better optics as FPL53, despite its very slightly inferior Abbe number, because it can be polished to a smoother surface. O'hara's website says 55 has improved polishing characteristics and abrasion values. I have no personal expertise or experience to verify, it's an interesting possibility though.

#7 Kent10

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Posted 15 June 2017 - 05:11 PM

I was told by one high-end apo maker that FPL55 could result in just as good or better optics as FPL53, despite its very slightly inferior Abbe number, because it can be polished to a smoother surface. O'hara's website says 55 has improved polishing characteristics and abrasion values. I have no personal expertise or experience to verify, it's an interesting possibility though.

Interesting.  I have wondered how exactly FPL55 glass differs from FPL53.  If FPL53 is obviously superior to FPL51 than you might think (perhaps erroneously) that FPL55 is "better" than FPL53.  But I am sure it is not simple and as you suggest, John, there might be some features that are better and others that are not.  Yuri and other makers have to decide what is best for them.  I wonder why Ohara is moving away from FPL53.  Is it too expensive or do they feel FPL55 is better for the same cost?



#8 Kent10

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Posted 15 June 2017 - 05:24 PM

Isn't it a bit of a stretch to refer to FPL55 as a "lesser glass? Correct me if I'm wrong but isn't that what CFF uses in their larger scopes? Another question aren't fpl53 and FPL55 almost the same and in this context to be fair they are both lesser when compared to fluorite? Just a few things to ponder but I wouldn't consider a FPL55 based TEC 140 as a lesser instrument than the current version.

I think you are right.  I can speak for myself that I don't know if FPL55 is a lesser glass and if you look at the chart Yuri provided, color correction is very close to FPL53.  As John said, color correction isn't the only consideration in quality of glass.  Yuri says he would choose Fluorite for the 140 because it “has more margin of safety.” I don't think he suggested it was because FPL55 is not a good glass.  I probably shouldn't have used the word "lesser" for FPL55.  I put it in parentheses because I wasn't sure but still I think it was a bad choice of words since I don't really know.  



#9 Kent10

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Posted 15 June 2017 - 05:29 PM

I went back to read the Tec thread some more. 

 

This is Yuri's question as to which option a customer would choose.

 

"Losing a bit of performance for cheaper glass  (FPL55 vs. FPL53) or getting better performance for more expansive CaF2?"

 

https://groups.io/g/...s/message/27694



#10 Headshot

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Posted 15 June 2017 - 06:30 PM

Is there any indication how Roland is going to cope with the demise of FPL53 in the optical design the AP130GTX?

 

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#11 Scott in NC

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Posted 15 June 2017 - 08:37 PM

Is there any indication how Roland is going to cope with the demise of FPL53 in the optical design the AP130GTX?

 

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Hopefully not by changing AP to a "mounts only" company, or worse, by retiring. bigshock.gif



#12 sewhite

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Posted 15 June 2017 - 09:09 PM

Is there any indication how Roland is going to cope with the demise of FPL53 in the optical design the AP130GTX?

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Roland, cope? He will probably find a new way to exploit FPL55' properties. Yes, he will cope.

Stan

#13 sparrowhawk

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Posted 15 June 2017 - 09:48 PM

I wonder how this will affect the other market players like Stellarvue, WO, Skywatcher, etc?

Shawn

#14 elwaine

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Posted 15 June 2017 - 10:08 PM

To boil down a question I asked on the TEC forum (but to which I have received no meaningful answers), are there any real world practical differences in the final processed astrophotograph, whether the refractor used to acquire the images has FPL-53, FPL-55, or Fluorite? 

 

Theoretical discussions of optics under laboratory conditions are always fun and informative. But I wouldn't want to spend extra money for an optic whose theoretical superiority is cancelled out by the atmosphere.

 

I know there are some very skilled astrophotographers in this forum. What say you?. 


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#15 Suavi

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Posted 15 June 2017 - 10:33 PM

I wouldn't be surprised if dust and pollen that sets on the front of the lens just after one stargazing session would cause more light scatter than differences between FPL53/55/fluorite.


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#16 Jared

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Posted 16 June 2017 - 12:40 AM

The short answer to the question of whether one could tell the difference in the real world, assuming you are talking about prime focus long exposure astrophotography, is probably not. On a good night I get 2 arc second stars out of my 130mm refractor over a five minute exposure. On the best nights it's more like 1.8" stars (full width/half maximum measurements). That is still substantially larger than the Airy disk. Seeing conditions will still dominate in terms of resolution. Even if polychromatic Strehl drops a touch I doubt Inwould ever know it. Worst case they just tweak the focal ratio a touch, I expect. Oh, and I doubt the harder surface of 55 will be much of a benefitbfor low volume telescope makers. It will matter more to someone working at higher volumes where being able to polish at a faster speed is a benefit.

Edited by Jared, 16 June 2017 - 12:42 AM.

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#17 elwaine

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Posted 16 June 2017 - 07:54 AM

The short answer to the question of whether one could tell the difference in the real world, assuming you are talking about prime focus long exposure astrophotography, is probably not. On a good night I get 2 arc second stars out of my 130mm refractor over a five minute exposure. On the best nights it's more like 1.8" stars (full width/half maximum measurements). That is still substantially larger than the Airy disk. Seeing conditions will still dominate in terms of resolution. Even if polychromatic Strehl drops a touch I doubt Inwould ever know it. Worst case they just tweak the focal ratio a touch, I expect. Oh, and I doubt the harder surface of 55 will be much of a benefitbfor low volume telescope makers. It will matter more to someone working at higher volumes where being able to polish at a faster speed is a benefit.

 

Thanks Jared!!!

 

As for the "harder glass," you are spot on. Yuri said, "Harder glass for faster polishing? - that makes no difference for us since we are not using polishing pads and fast polishing techniques."



#18 vahe

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Posted 16 June 2017 - 08:44 AM

Aside from its performance the real reason why TEC140 turned out to be such a big hit was its price point, the fact that TEC managed to offer their 140 at such a low price helped make it a real success,

.
I can see that for Yuri to consider fluorite and raising the price of this bargain APO, at the minimum, should give him a pause, will the newer 140FL continue to sell like the older model?

.
Just compare the TEC140 to AP140 in price category to see why TEC is so popular.

.

Vahe


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#19 Jon_Doh

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Posted 16 June 2017 - 09:52 AM

I wonder how this will affect the other market players like Stellarvue, WO, Skywatcher, etc?

Shawn

I've wondered the same thing.  What about switching to Hoya's FCD100 glass, a clone of FPL-53?  It has an Abbe rating around 95.  

http://www.optoglass...ts?id=1&i=3&m=1


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#20 CounterWeight

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Posted 16 June 2017 - 11:04 AM

My standard response to glass discussions here is usually that IMO it is more about the 'who' is making the scope and what they let out the door to customers than the 'what' exactly the glass types are. There are others considerations here as far as lens cell design and spacing, focal ratio's... visual only or visual and imaging... manufacturability of final design to market price...  I know it's an assumption on my part but I suspect that whatever Yuri / TEC, Caitlin / CFF, Roland / AP, or other high end scope designers choose they will make work for their customers to the best of their ability.


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#21 Schubert

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Posted 16 June 2017 - 12:28 PM

As far as I understand it´s FPL55 which makes it possible for CFF to make such large Apo´s.
FPL53 was very difficult to obtain in blanks larger than 7 inches



#22 Wildetelescope

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Posted 16 June 2017 - 01:05 PM

Isn't it a bit of a stretch to refer to FPL55 as a "lesser glass? Correct me if I'm wrong but isn't that what CFF uses in their larger scopes? Another question aren't fpl53 and FPL55 almost the same and in this context to be fair they are both lesser when compared to fluorite? Just a few things to ponder but I wouldn't consider a FPL55 based TEC 140 as a lesser instrument than the current version.

As Yuri, Roland and others have stated often, it is not so much about the glass in one element as much as how each of  the elements in the triplet are matched in the design that determines the performance.   It also determines the Cost, which as others have stated here, is the real issue with going to the different materials. I am sure that Yuri and Roland can make excellent optics with whatever glass options are available.  Whether or not I could afford them is a different question all together:-)

 

Cheers!

 

JMD


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#23 Jon_Doh

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Posted 16 June 2017 - 02:29 PM

 

Isn't it a bit of a stretch to refer to FPL55 as a "lesser glass? Correct me if I'm wrong but isn't that what CFF uses in their larger scopes? Another question aren't fpl53 and FPL55 almost the same and in this context to be fair they are both lesser when compared to fluorite? Just a few things to ponder but I wouldn't consider a FPL55 based TEC 140 as a lesser instrument than the current version.

As Yuri, Roland and others have stated often, it is not so much about the glass in one element as much as how each of  the elements in the triplet are matched in the design that determines the performance.   It also determines the Cost, which as others have stated here, is the real issue with going to the different materials. I am sure that Yuri and Roland can make excellent optics with whatever glass options are available.  Whether or not I could afford them is a different question all together:-)

 

Cheers!

 

JMD

 

This is true as well as how the glass is finished and spaced.  However, there is something for the type of glass used or else the high end scope makers would have been using FPL-51 glass already since it's a lot cheaper than FPL-53.  


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#24 CounterWeight

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Posted 16 June 2017 - 02:49 PM

My TEC APO 160ED was FPL51 and it was a fantastic optic!  Yes it was f/8... and something I read a long while ago stated that FPL53 and Fluorite could more easily lend themselves to faster ratios (I may be able to find and cite source if mandatory but I believe it was in a paper by TB or RC ?), for '51' f/8 was about it.  This is a complex topic.  As I mentioned in prev. post there is a lot to consider in any scope design and it's difficult to armchair the subject, even though my maxim about who over what may be doing exactly that.



#25 Kent10

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Posted 16 June 2017 - 02:59 PM

Yes, I believe that is why the Tec 200FL is F8 and the Tec 200ED is F9.  And the F9 version is still not as well corrected for color as the F8 Fluorite.  Yuri did consider a 200FL F7 with different glasses but it never happened.




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