Re: [ATM] Am I there yet?

[Mark Cowan <toolontop@yahoo.com>]

Hi Don:

Frankly, I wouldn't do either of those things you
suggest.  One of my concerns about the previous post
and your test numbers is the fairly wide spread on
them - you're likely not getting a true (or at least
repeatable - either will do for figuring) reading of
the actual surface.  Your photo shows a fair amount of
small scale roughness and this can make it very hard
to read reliable for the overall correction.  OTOH
I've seen far worse... ;)  Not saying it's good or
bad, it's just there.  The only real cure is a lap
that smooths it, but see below.

In the photo I see a fairly narrow (1/4-3/8") edge
defect that is variable in width but not too bad for a
mirror of this f/ratio.  It's almost like it turns
then flattens out at that point, wouldn't surprise me,
it's hard to see though.

I concur with Jim this time and think your best step
would be to stop and call it done.  Put it in use,
play with edge masking, get a feeling for how well it
works.  Your motivation to exceed it on the next try
will be eased by the fact that you will be /starting
fresh/ and that, plus the distance in time, will get
you better results and more knowledge than if you
experiment on what appears to be a pretty nice mirror.

CHeers,
Mark Cowan
Salem, OR USA

Donkey:  "Did ya hear that Shrek?  He called me a
Guru!"
Shrek:   "Really?"

--- Don Bates <dbates59@yahoo.com> wrote:

> Bob, Mark, Dale, and other Mirror Gurus:
> 
> Please take a minute to give me your opinion on the
> condition of my 10-inch f/6.6 thin plate glass
> mirror
> that is nearing completion. Sorry about not being
> able
> to see the images of my  mirror project in my last
> message. I just figured out how to upload my images
> to
> the atm file area. The links below should work.
> 
> Here is a general look at the surface condition
> using
> the Foucault test:
>
http://www.atmlist.net/contrib/dbates59-at-yahoo-dot-com/Bates10inch/09_08_2004/Bates1.jpg
<snip> 
> Here is what I think I need to do:
> 1) Push down the 85% zone with TOT, edge of tool
> over
> 85% zone. 
> 2) Push down the center some more with TOT, edge
> over
> center area.
> 
> Questions:
> 1) Are my plans for the next figuring session
> correct?
> <snip>


		
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