Re: [ATM] Mirror back from coaters with scratches

[Dominic-Luc Webb <dlwebb@canit.se>]

Ohayoo Hiroyuki!

Normally, I would say scratches do not matter much, but the
astronomical dimensions 2"x1" you state are more than just
a scratch. Could you please resend numbers. In terms of knowing
if this reached the glass, it might be obvious if the scratch
has any depth at all, because mirror coatings are typically very
thin. I could guess somewhere around 50-100 nm.

Yoi ichinichi o!

Dominic-Luc Webb


On Fri, 25 Aug 2006, Hiroyuki HIKITA wrote:

> Hi all!
>
> Lots of wandering through the ATM archives and sheer luck,
> my second attempt to make a 6" F6 mirror came out very well
> with a smooth surface and Waveerror P/V 1/20 Lambda.
>
> Two weeks ago I sent out my second mirror to the coaters.
> Today my 6inch F6 mirror came back from the coaters.
>
> Lesson: NEVER use a cheap coater just to save $50...
>
> The mirror came back with several S shaped scratches about
> 2"x1" in size.
>
> So my question is:
> 1) How obvious are scratches this size under the Foucault test?
>    Could I have missed it under the knife??
>
> 2) Is there a quick way to tell if the scratches went all the way to the glass?
>
> # Hiroyuki HIKITA <hikita@tkb.att.ne.jp>
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> ATM mailing list http://www.atmlist.net/
>

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