From: "mlbrown{at}everstrive.com" 
To: atm{at}shore.net
Reply-To: "mlbrown{at}everstrive.com" 


Note large chip at top of 6" f/8 mirror.  Gives excellent images,
despite the rough newbie surface.

http://host67.everstrive.com/~mlbrown/ASTRONOMY/FoucaultTest6s.jpg

This chip has a story behind it;  gives the mirror CHARACTER.

=Matt



Original Message:
-----------------
From: Frank Q frank{at}katestone.com.au
Date: Wed, 26 Mar 2003 08:52:23 +1000
To: scottythefiddler{at}cogeco.ca, dan_douglas_{at}hotmail.com, atm{at}shore.net
Subject: Re: ATM thin mirror, hogging with partially hogged surface on
other side



Hi Daniel / All

I agree with "scottythefiddler" on this one. A chip 1/4"
across at this stage
is not worth worrying about. By the time you put on a decent bevel and finish
the rough grinding, most of it will probably be gone.

I've had my share of chipped (and dropped !!!!!!!) mirrors. A 6" had 2
chips on its finished aluminised surface (it looked like someone drilled
two 1/2" holes
on the edge) but this didn't affect the performance. The 8" I'm
currently regrinding
got a chip taken out of the side which extended about 1/8" into the surface. The
tool got stuck during the final fine grinding stages and I damaged it while
separating
them. So I got a grinding stone (the ones they use to sharpen chisels) and
ground a flat
spot on the side of the mirror. If anything, it gives the mirror a bit of character!!

But -- keep us updated as I'm sure there's lots of ATMers out there who are
interested in thin mirrors.

Cheers
Frank Q




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