Re: [ATM] Plastic.....

[<fundo@bellsouth.net>]

> To all on the list,  until polycarbonite lenes become more consistant with 
> eyeglasses I will not trust them for magnifications beyond my nose..... Polycarbonites 
> are amazing, and I love my eyeglasses, so that if a projectile strike's the 
> surface of my eyeglass I don't have shard's of glass entering my eye....
>      But I have yet to see a 6" refractor's primary len's made of this 
> substance, or it's air tight mate on the back side. And also can you imagine 
> a 16" (polycarbonite base) mirror in a telescope that has a parabolic shape 
> to come anywhere near what glass can do?  I have asked this question before 
> and someone gave me an answer..... and someone has done it but..... It is 
> experimental.......
>     Believe me I will be first in line when someone starts selling 
> Polycarbonite mirror blanks!!!!!!!!!!!!!

Russ,  Additionally, most plastics absorb a considerable amount of H2O.  We went over this several years ago, and I was surprised at the water entrainment (?) capacity of some common plastics.  

As for your eyeglasses........don't ever put one under a Ronchi or Foucault test!!!!  Just for kicks some years ago, I checked mine.........let me tell you....they ain't 1/20 wave!!! <G>

*****-----
Dan F.
Memphis, TN

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