Re: [ATM] Glass type

["lance clarke" <alaskawolfjoe@hotmail.com>]

The glass is 4.5" in diameter, and the bk7 is 1/2" at the edge and almost 1" 
in the center (plano-convex).  The sk-16 is the same diameter, but almost 
1-1/4" thick with a plano-concave configuration (flat side is actually a 
little convex). I've always wanted to try my hand at an achromat someday, 
and the glass was cheap (and like I said before, I can always make them into 
a mirror).

Now, one more question;  My understanding is that bk7 is borosilicate, same 
as pyrex.  What do they do differently to make optical glass? Is it quality 
of ingredients? Technique? Both?
And what exactly does "crown glass" mean?

Lance

>I would say find a flint to go with either one of the glasses you have and
>make a doublet.
>
>What are the dimensions of the glass?
>
>Jerry
>
>
>
>-----Original Message-----
>From: lance clarke
>
>Hi,
>I just picked up some optical glass that seems like it might be possible to
>use in a refractor.
>One piece is BK-7 (or N-BK7...is there a difference?) and the other appears
>to be N-SK16.  However, these pieces are not documented, I'm just going by
>the glass codes.
>
>


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