From: Mark Holm 
To: ShooterBall{at}hotmail.com, atm{at}shore.net
Reply-To: Mark Holm 


Hi Rich,

1.  Five zones isn't too many.  I used 4, then 8 and finally 10 while working on
an 8" f/6.  The last two of the ten were narrow zones placed very near the edge,
because I was working back form a turned edge, and need to have good data
there to know what was going on.  8 zones on two Couder masks is about
right for figuring an 8" f6 using a data reduction program.  (My
opinion.)

You can ease the task of laying out the masks by downloading my Couder Mask
program  http://www.atmsite.org/contrib/Holm/coudermask/couderma.html 
(Windows program only)  This program uses the latest zone math by Nils Olof
Carlin.  See the math at http://www.atmsite.org/contrib/Carlin/couder/ 
(Javascript - runs in
most browsers.)


2. You need to use a Foucault data reduction program.  I recommend Sixtests
by Jim Burrows. 
http://home.earthlink.net/~burrjaw/atm/atm_math.lwp/atm_math.htm.
  If at all possible, use the Windows version.  It is the most up to date.

It is certainly possible to make a good mirror without a data reduction program,
but why?  Sixtests is, in my opinion, the best for typical ATM use.  A nice
balance of sophisticated math underneath with a fairly easy user interface
on top.

Sixtests does require us inch oriented people to convert to millimeters. 
It is definitely worth the extra trouble.  It is also a Windows program.

3. Here is an example of Sixtests output using the Foucault data you posted
on the atm list for your 8" f6 mirror.
http://pong.telerama.com/~mdholm/atm/RichMirror/RichMirror.html

It shows you are elliptical, about 1/2 way between sphere and parabola.

4.  Try to turn off the HTML in your e-mail program when you compose a
message to the atm list.  The HTML really clutters up the digest version.

5.  Don't be bashful about asking for more help on this list as you work on your
mirror and scope.

Mark Holm
mdholm{at}telerama.com

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