Re: [ATM] Two mirrors on one tool

["James Lerch" <jlerch1@tampabay.rr.com>]

----- Original Message ----- 
From: "Paul Bradley" <paul@paul-bradley.com>

>
> I've read about people who have done this by using the same tool and doing 
> alternate wets on
> each mirror. That's what I'm doing, but some people said to alternate MOT and 
> TOT as well.
>
> Wouldn't this tend to keep the focal length around where it is? I've been 
> working exclusively MOT.

Hi Paul,

On my 8" f/8 Bino's I used the same tool (and lap) on both mirrors.  I started 
off MOT for both mirror's until I reached the desired focal length.  Once the 
desired focal length was achieved I started alternating between MOT & TOT to 
keep the focal length constant (or nearly constant).  If the focal length 
started getting long I'd favor MOT, and vice versa.

One item of interest, when the day comes that your ready to take both mirrors 
past 25 micron grit, try and set aside enough time to finish fine grinding both 
that day.  Stopping at 9 micron and restarting again the next day has never 
worked out very well for me, and usually results with the tool getting stuck to 
the mirror.  (BTW, when this happens, just stop and soak the mirror / tool for 
several hours in a bucket of room temp water, they will eventually just slide 
apart)


Take Care,
James Lerch
http://lerch.no-ip.com/atm (My telescope construction,testing, and coating site)
http://lerch.no-ip.com/ChangFa_Gen (My 15KW generator project)

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