Re: [ATM] SK14 Glass

["Bob May" <bobmay@nethere.com>]

SK series glasses are refractive optics purpose glasses in the position
between the crown and flints.  The generic name early on was "Short Krown".
The glass is well off of the normal glass line which means that it is quite
able to do a better correction of the color error in refractive optics than
glasses that are near the normal line of glasses.
The "normal line" of glasses is the line of the refractive index vs. the
Abbe number of the glass that most of the easily made glasses fall near.
Glasses that are near the line will generate a color correction of a certain
level of correction.  Getting a glass that is distant from the normal line
can allow for much better correction of the color error.
The SK line of glasses generically have a moderately poor resistance to
corrosion and staining so they really shouldn't be used as an exterior
element in a lens.  They also fracture easily so their use as a mirror
substrate isn't recommended along with a large expansion coefficient which
means that you really don't want to use it as a mirror substrate as the
glass is just as bad as plate glass but costs a lot more.
Bob May
http://nav.to/bobmay
bobmay@nethere.com
NEW! http://bobmay.astronomy.net


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