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Equipment Discussions >> Refractors

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10gauge
sage


Reged: 10/31/10

Loc: Boston
Declining Quality of Premium Optical Glass
      #5528814 - 11/19/12 09:08 PM

There seems to be an alarming trend in securing premium optical glass for us refractorphiles. Summarizing from a few threads in the Yahoo TEC Group, Yuri has seen an increase in the rejection ratios of premium glass. It appears that the quality of CaF2 and FPL53 premium glass is not what it was 10 years ago. He is having to send lenses back to Ohara for visible striae in artificial star tests. In another thread he stated that he is not taking any new orders for the APO 160FL at this time. He feels that the quality of large lenses are in decline, even to the point of shifting production to reflectors if the situation does not improve. That would be a sad day. How do people feel about the future trends, philosophy, and quality of optical glass?...

http://tech.dir.groups.yahoo.com/group/tec-scopes/message/22839

I also noticed that the TEC 140 is now $5,700, up from $5,500. I ordered my TEC 140 a year ago, and I still haven't received it yet. Yuri said it would be done in 6 months as there were 50 people ahead of me. I am getting a little nervous... I am crossing my fingers, hoping I don't get the bottom batch of glass.


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Sky Muse
sage


Reged: 10/26/12

Loc: De Soto County, MS
Re: Declining Quality of Premium Optical Glass new [Re: 10gauge]
      #5528863 - 11/19/12 09:34 PM

Within this review of the Takahashi FS-78, about a third of the way down, there is a very interesting read about calcium fluorite crystal...

http://scopeviews.co.uk/TelescopeReviews.htm#_Takahashi_FS78

I read it just today, and it finally confirmed my suspicion as to why Takahashi practically abandoned calcium fluorite for its objectives.

Alan


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Danno2006
Pooh-Bah


Reged: 01/25/06

Loc: Ontario, Canada
Re: Declining Quality of Premium Optical Glass new [Re: Sky Muse]
      #5528920 - 11/19/12 09:59 PM

I owned a TEC140, bought a C14 and the TEC140 stayed in its case until I sold it. I moved away from a quality refractor and have not looked back. Given glass availability, LZOS may be the last manufacturer remaining making larger than 150mm premium quality, triplet refractors. I can't wait to see what kind of quality and aperature that Yuri can put into a compound mirror scope at the price point of a TEC180. Just noticed a 30" Starmaster dob at another site at the same price as the TEC180 tube - and the dob is mounted. The writing is on the wall, the king is dead, long live the new king.

Edited by Danno2006 (11/19/12 10:00 PM)


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Sky Muse
sage


Reged: 10/26/12

Loc: De Soto County, MS
Re: Declining Quality of Premium Optical Glass new [Re: Danno2006]
      #5528985 - 11/19/12 10:30 PM

"The writing is on the wall, the king is dead, long live the new king."

Might one suggest, analogously, the abandonment of a succinct novel in favour of comics.

Alan


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BillP
Postmaster
*****

Reged: 11/26/06

Loc: Vienna, VA
Re: Declining Quality of Premium Optical Glass new [Re: Sky Muse]
      #5529004 - 11/19/12 10:37 PM

Hopefully the Tak glass will stay high quality as I believe their lenses are made for them by Canon and Canon pours its own glass.

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vahe
scholastic sledgehammer


Reged: 08/27/05

Loc: Houston, Texas
Re: Declining Quality of Premium Optical Glass new [Re: 10gauge]
      #5529006 - 11/19/12 10:39 PM

Quote:

It appears that the quality of CaF2 and FPL53 premium glass is not what it was 10 years ago. He is having to send lenses back to Ohara for visible striae in artificial star tests. In another thread he stated that he is not taking any new orders for the APO 160FL at this time. He feels that the quality of large lenses are in decline, even to the point of shifting production to reflectors if the situation does not improve.






When the word got around that TEC was not producing larger apos I asked Yuri if fluorite quality was the reason, he said that the reason was the quality of mating elements and not the fluorite. Fluorite is available in larger sizes with the problem being the price which is astronomical.
FPL-53 has always been a problem with nominal 6” being its practical limit.

In another thread Yuri indicated that one of the reasons for not producing Maksutovs, again, is the glass quality needed for the meniscus. Using premium quality glass, which by the way is available, would increase the price of his 10” Mak to near 180FL price level.

Vahe


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Sky Muse
sage


Reged: 10/26/12

Loc: De Soto County, MS
Re: Declining Quality of Premium Optical Glass new [Re: BillP]
      #5529158 - 11/19/12 11:54 PM

Canon made the calcium fluorite lens of my FS-102.

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chboss
professor emeritus


Reged: 03/24/08

Loc: Zurich Switzerland
Re: Declining Quality of Premium Optical Glass new [Re: Sky Muse]
      #5529169 - 11/19/12 11:58 PM

Canon-Optron to be precise:
http://www.canon-optron.co.jp/english/

best regards
Chris


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Sky Muse
sage


Reged: 10/26/12

Loc: De Soto County, MS
Re: Declining Quality of Premium Optical Glass new [Re: chboss]
      #5529957 - 11/20/12 11:53 AM

When I purchased my apochromat in 2003, the A-P "Traveler" was out of the question given its limited availability and higher cost, and the TeleVue offerings with their "warm" views were never even considered. The FS-102 was on sale for $1899 at the time, and from Texas Nautical Repair...how could I resist? No matter, for while I might've strived towards purchasing the "Traveler", and in all probability, successfully, I had chanced upon this prior to making my decision...

http://www.scopereviews.com/aptak.html

I knew that it was special, but until recent light, I never knew just how special, and unique compared to the vast majority of all other apochromats.

And to think that so many owners of the FS series have sold and are presently selling off these true fluorite gems, for even less than what they paid when new, and for whatever reason, is nothing short of tragic.

Regards,

Alan


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jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: Declining Quality of Premium Optical Glass new [Re: Sky Muse]
      #5530078 - 11/20/12 12:48 PM

Fluorite optical glass is in reasonable supply and quality remains high. In fact, for large blanks this is the only reliable way to go unless you make your own ED glass as LZOS does.

I like the FS-series scopes, and have one now, and have had a couple of others. However, above 4" I don't find them to be particularly well color corrected visually. Even at 4" I can coax in-focus false color that is just detectable on very bright targets like Vega, Venus and Sirius. The 3" remains visually color free, but that's simply a function of the constant f/8 focal ratio for the line and the declining aperture.

That said, color correction isn't the do all to end all anyway. I find the figure quality on the FS scopes to be quite good, and the simple doublet design using extremely homogeneous fluorite scatters very little compared to harder glass doublets and triplets.

They're nice scopes. But even when they were being cleared out, they were relatively expensive given that they were totally "ala carte" and Tak accesories (clamshells, finders, etc.) are ridiculously expensive.

I also agree that folks selling them now are nuts. Hang on to them. The fluorite doublet is not coming back. As doublets go, these are about the ultimate iteration of the concept; the pinnacle of doublet refractor evolution.

Regards,

Jim


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Sky Muse
sage


Reged: 10/26/12

Loc: De Soto County, MS
Re: Declining Quality of Premium Optical Glass new [Re: jrbarnett]
      #5530199 - 11/20/12 01:36 PM

This morning I was mindful of the overlooked rear element within mine, as I understand it's well-matched to the fluorite, its high quality necessary even to that of the front element's performance, and in tandem to the doublet overall, so I've read, but I'm still unaware of its type.

Regards,

Alan


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Paul G
Post Laureate
*****

Reged: 05/08/03

Loc: Freedonia
Re: Declining Quality of Premium Optical Glass new [Re: jrbarnett]
      #5530245 - 11/20/12 01:58 PM

Quote:

Fluorite optical glass is in reasonable supply and quality remains high. In fact, for large blanks this is the only reliable way to go unless you make your own ED glass as LZOS does.

I like the FS-series scopes, and have one now, and have had a couple of others. However, above 4" I don't find them to be particularly well color corrected visually. Even at 4" I can coax in-focus false color that is just detectable on very bright targets like Vega, Venus and Sirius. The 3" remains visually color free, but that's simply a function of the constant f/8 focal ratio for the line and the declining aperture.

That said, color correction isn't the do all to end all anyway. I find the figure quality on the FS scopes to be quite good, and the simple doublet design using extremely homogeneous fluorite scatters very little compared to harder glass doublets and triplets.

They're nice scopes. But even when they were being cleared out, they were relatively expensive given that they were totally "ala carte" and Tak accesories (clamshells, finders, etc.) are ridiculously expensive.

I also agree that folks selling them now are nuts. Hang on to them. The fluorite doublet is not coming back. As doublets go, these are about the ultimate iteration of the concept; the pinnacle of doublet refractor evolution.

Regards,

Jim




I agree, they are very nice scopes. I had an FS128 and enjoyed using it. As you noted the false color is there if you know where to look, particularly if you have a color free scope to side by side with it. It also contributes to the "warm" tone the image has in the FS (blue is out of focus). If I had not been offered an AP 130 EDF I would not have sold the FS.


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RodgerHouTex
Pooh-Bah
*****

Reged: 06/02/09

Loc: Houston, Texas, USA
Re: Declining Quality of Premium Optical Glass new [Re: Paul G]
      #5530354 - 11/20/12 02:51 PM

I intend to be buried with my FS-152!

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TG
Pooh-Bah


Reged: 11/02/06

Loc: Latitude 47
Re: Declining Quality of Premium Optical Glass new [Re: 10gauge]
      #5530450 - 11/20/12 03:39 PM

Quote:

... He feels that the quality of large lenses are in decline, even to the point of shifting production to reflectors if the situation does not improve. That would be a sad day. How do people feel about the future trends, philosophy, and quality of optical glass?...





The real sad day for me was when I found out that TEC was no longer making their Maks. So you're saying there is hope yet!

Tanveer.


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Jarno
member


Reged: 05/22/05

Loc: Netherlands
Re: Declining Quality of Premium Optical Glass new [Re: jrbarnett]
      #5530628 - 11/20/12 05:00 PM

Quote:


I also agree that folks selling them now are nuts. Hang on to them. The fluorite doublet is not coming back.




A couple of years ago I bought a Vixen FL102 which uses the same Canon/Optron optics. If you ever see my scope for sale you'll know I'm either six feet under or own its Tak half-brother. 'Nuff said.


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Sky Muse
sage


Reged: 10/26/12

Loc: De Soto County, MS
Re: Declining Quality of Premium Optical Glass new [Re: RodgerHouTex]
      #5530658 - 11/20/12 05:23 PM

I second that!

Alan


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M13 Observer
scholastic sledgehammer


Reged: 12/09/06

Re: Declining Quality of Premium Optical Glass new [Re: TG]
      #5530683 - 11/20/12 05:36 PM

Quote:

Quote:

... He feels that the quality of large lenses are in decline, even to the point of shifting production to reflectors if the situation does not improve. That would be a sad day. How do people feel about the future trends, philosophy, and quality of optical glass?...





The real sad day for me was when I found out that TEC was no longer making their Maks. So you're saying there is hope yet!

Tanveer.




I think Yuri said that the glass for the miniscus was getting incredibly expensive and he did not feel that there was a sufficient interest in an expensive Mak. He was thinking about making shorter focal length reflectors with near focus refractive corrector type systems instead, or something to that effect. One never knows until it is actually produced though.


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TG
Pooh-Bah


Reged: 11/02/06

Loc: Latitude 47
Re: Declining Quality of Premium Optical Glass new [Re: M13 Observer]
      #5530747 - 11/20/12 06:14 PM

Quote:

I think Yuri said that the glass for the miniscus was getting incredibly expensive and he did not feel that there was a sufficient interest in an expensive Mak.




The first part doesn't seem right as the meniscus is just BK7, the cheapest optical glass on the planet.

The second part I can agree with as Maks appeal to a limited segment except when it's the A-P Mak in which case everybody wants one.

Tanveer.


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vahe
scholastic sledgehammer


Reged: 08/27/05

Loc: Houston, Texas
Re: Declining Quality of Premium Optical Glass new [Re: TG]
      #5530819 - 11/20/12 06:53 PM

Quote:

The first part doesn't seem right as the meniscus is just BK7, the cheapest optical glass on the planet.





Check out post #19837 on tec-ug.

Vahe


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10gauge
sage


Reged: 10/31/10

Loc: Boston
Re: Declining Quality of Premium Optical Glass [Re: vahe]
      #5531333 - 11/20/12 11:40 PM

Why are prices for premium glass expanding faster than the universe? The chemistry hasn't changed much, contrary to the fact that production techniques have improved and should have become cheaper over the years. Is it demand, labor, raw materials, facilities, or is it simply because that people will pay for such premium glass?

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