From: Aplanatic{at}aol.com
To: atm{at}shore.net
Reply-To: Aplanatic{at}aol.com


Hello Mark,

Frankly, I was a bit baffled by your post.  Having read and enjoyed many of
your posts in the past, this email seems uncharacteristic of your usual
clear and careful thinking.

You can test Foucault data reduction programs for yourself, as I did
extensively for Figure before releasing it in its first (DOS) version,
circa 2000:  Create a radial surface profile for a fictitious mirror,
calculate the longitudinal aberration for a set of zonal radii, plug the
numbers into the program and calculate the difference between the predicted
and constructed surfaces.  If you had done this with Sixtests, Figure and
TEX, I think you'd find very little difference between the three, at least
for relatively low-order constructed surfaces where the test makes sense to
apply.

Mark Holm wrote:

> In my not so humble opinion, this is a mistake.  Jim Burrows knows his math
and
> did a lot of clear thinking on Sixtests.  The result shows it.  Sixtests is
the
> best.  At this time using any other of the free programs available to ATM's
> isn't a smart idea.

A lot of thought, care and testing was also put into Figure.  Why is it not
a smart idea to use it?

Interestingly, Jim Burrows had a significant role in the development of Figure.
 He often was my sounding board for subtle issues, and he tested the program
for me on several occasions.  Many thanks to you, Jim.

James Lerch converted Figure45 (the original, DOS version) into FigureXP,
which now runs on Windows.  I ran all of my old test cases against the beta
version of FigureXP and found the calculations to be identical with the
original version.  It is computationally sound.

Figure has a much different human interface than TEX or Sixtests.  This may
be of value to some users.  In addition, it performs some calculations that
Sixtests does not perform.  These additional features might be of interest.
 On the other hand, Sixtests can analyze data from a variety of other
mirror tests, which Figure does not do.

If they give sound results, is it not better to have several options? 
After all, the programs are freeware and were developed primarily for your
use and enjoyment.

My best,
Dave Rowe

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