Re: What is ED glass?

From: Chris1011 (chris1011_at_aol.com)
Date: 12/14/04 

Date: 14 Dec 2004 15:33:03 GMT

>Oooops, lower reftractive index.
>>What is the meaning of the diagram >here>
>http://www.optcorp.com/product.aspx?pid=383-405-1844

What is ED glass? This term is applied to any glass which has a reciprocal
dispersion number of 70 or greater. The higher this number, the less the glass
will disperse the colors of the spectrum. The ED designation includes fluorite
and fluorite analogs such as FPL53, CaFK53 and FCD100.

All these materials have the POTENTIAL to reduce the overall color error in a
doublet or triplet lens. I say potential, because the actual correction of the
color error falls to the mating element, not the ED or fluorite. With the
proper mating element, even the lowest ED glass FK01 can result in a completely
color-free lens. Furthermore, with the use of a non-ideal mating element, even
a fluorite lens can have color error in the blue-violet, which is the case with
the FS series of fluorites.

Roland Christen

Relevant Pages

  • Re: What is ED glass?
    ... > dispersion number of 70 or greater. ... > color error falls to the mating element, not the ED or fluorite. ... even the lowest ED glass FK01 can result in a ...
    (sci.astro.amateur)
  • Re: What is ED glass?
    ... This term is applied to any glass which has a reciprocal ... > color error falls to the mating element, not the ED or fluorite. ...
    (sci.astro.amateur)
  • Re: spotting scope question-specific
    ... If you find a used apo scope ... in your price range, don't hold out for something more modern. ... Not much of the cost of a good lens, let alone a scope, is in the glass. ... Fluorite is a mineral, calcium fluoride. ...
    (rec.birds)
  • Re: Need Cylinder Lens specs -
    ... BK7 is the common standard glass used around the world. ... >>cylindrical lens that comes with the S t a r S p e c t r o s cope. ... "To obtain greater dispersion you can either ... > use a shorter focus eyepiece OR place the grating farther away from the ...
    (sci.astro)
  • Re: Canon - Nikon Observations
    ... So that's your criteria for choosing lenses, which ones will work in space? ... Nikon developed ED glass to enable the ... However, fluorite easily ...
    (rec.photo.digital)