ATM [Fwd: BOUNCE atm@shore.net: Non-member submission from [John Vogt <atmer@idt.net>]]

[Mel Bartels <mbartels@efn.org>]

> From: John Vogt <atmer@idt.net>
> Subject: Re: ATM Re: Composite Mirrors
>
> Daniel Fundo wrote:
>
> Has anyone on the list had experience with one of the fused pyrex blanks from
> the folks in Arizona or one of Newport's similar blanks?
>
> Dan- Have worked both Newport and Hextek blanks. The 24" Newport had little
> problem w/ printhrough and has been stable since 83'. Did a 30" of theirs
> that ultimately failed due to poor fusing. Took Newport 3-4 trys at that time
> (84-85) to come up w/ that blank. Had printhrough problems w/ the 30" due to
> thin front plate, had to regrind as Newport screwed up the slumping and wound
> up w/ a radius at about f/3- needed f/4.
> The Hextek blanks are beautifully made but very expensive and a real
> challenge to figure. Main problems are printhrough(what else!!) and
> astigmatism. These two problems quadrupled the time it took me to finish the
> mirrors. Oh yes, I had to do 2 32" mirrors as EMF coatings damaged the first
> one due to their stupidity.
>
> John



--
Clear skies, Mel Bartels
http://www.efn.org/~mbartels