Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Interesting info on ED glass in article about large compressor

  • Please log in to reply
6 replies to this topic

#1 RichA

RichA

    Surveyor 1

  • *****
  • topic starter
  • Posts: 1,690
  • Joined: 03 Jun 2010
  • Loc: Toronto, Canada

Posted 31 May 2020 - 11:28 PM

According to some of the notes in this article, the lowest dispersion glass grade that can be manufactured up to 32cm across without issues in Ohara's line is S-FPL51Y.  For this project, pure CaF was too expensive.  Raises interesting questions about the fabrication of large amateur apo refractors.  Such as where do they get high-grade FPL-53 or its equivalent?

 

https://www.research...ld_Imager_UHWFI

 

Unfortunately, most of the images I think were left out of the .pdf. 


Edited by RichA, 31 May 2020 - 11:29 PM.


#2 barbarosa

barbarosa

    Vanguard

  • *****
  • Posts: 2,496
  • Joined: 11 Apr 2010
  • Loc: 139 miles W of the Awahnee Hotel

Posted 01 June 2020 - 02:57 AM

"With a lens diameter of 32 cm and a thickness of 7.5 cm for the largest CaF2 lens" leads me to ask,

 

How many 320mm/ 12.5" APOs are sold every year?

 

Seriously though it is an Interesting article and thanks for finding it.



#3 Alan French

Alan French

    Night Owl

  • *****
  • Posts: 5,898
  • Joined: 28 Jan 2005
  • Loc: Upstate NY

Posted 01 June 2020 - 07:24 AM

The current pricing, according to the Ohara website, puts S-FPL51Y at 42.5 times the price of S-BSL7. The relatively new S-FPL55 is 15.5 times the price of S-BSL7, so FPL51Y is 2.7 times the price of FPL55.

 

Also the melt frequency for FPL51Y is "5," Lowest, while FPL55 is "1," Highest.

 

Clear skies, Alan



#4 RichA

RichA

    Surveyor 1

  • *****
  • topic starter
  • Posts: 1,690
  • Joined: 03 Jun 2010
  • Loc: Toronto, Canada

Posted 01 June 2020 - 10:07 AM

The current pricing, according to the Ohara website, puts S-FPL51Y at 42.5 times the price of S-BSL7. The relatively new S-FPL55 is 15.5 times the price of S-BSL7, so FPL51Y is 2.7 times the price of FPL55.

 

Also the melt frequency for FPL51Y is "5," Lowest, while FPL55 is "1," Highest.

 

Clear skies, Alan

So 51 is around $200/lb, if BSC is around $5.00/lb.  FPL-53 is about $350/lb.  I guess.



#5 Alan French

Alan French

    Night Owl

  • *****
  • Posts: 5,898
  • Joined: 28 Jan 2005
  • Loc: Upstate NY

Posted 01 June 2020 - 10:47 AM

So 51 is around $200/lb, if BSC is around $5.00/lb.  FPL-53 is about $350/lb.  I guess.

Huh? FPL-53 is 18x the price of S-BSL7, not much higher that FPL-55. Both are less than half the price of FPL-51Y.

 

I've heard FPL-53 is not really available.

 

Clear skies, Alan 



#6 RichA

RichA

    Surveyor 1

  • *****
  • topic starter
  • Posts: 1,690
  • Joined: 03 Jun 2010
  • Loc: Toronto, Canada

Posted 02 June 2020 - 12:06 AM

Sorry, I didn't think the "Y" meant a different glass than FPL-51.  I see in their tables it is and a lot costlier.  Any scopes using it?

 

https://www.oharacor...ncy-2018-01.pdf



#7 Riccardo_italy

Riccardo_italy

    Viking 1

  • -----
  • Posts: 854
  • Joined: 29 Sep 2014
  • Loc: Italy

Posted 02 June 2020 - 03:06 AM

It is not "up to 32cm". They required a lens of 32cm:

 

Our design now substitutes Ohara S-FPL51Y glass for CaF2. This glass is the lowest dispersion glass in Ohara’s product line that could be fabricated in the diameter required for UHWFI.

Additionally, the article has been submitted to arxiv on April 1th, 2006 (I hope it's not an April Fool's Day joke). I guess on 2006 FPL55 was not available.




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics