           TEX - MIRROR NUMBER CRUNCHING MADE EASY       Version 2.3

Tex is an MS DOS program that performs the tedious and error-prone
calculations required to reduce the Foucault knife edge readings to a 
quantitative measure of the surface profile and the wavefront accuracy.
Once the raw data has been entered, the user has three ways to evaluate
it:

1) Jean Texereau's algorithm, as described in his classic book, 
   "How to Make a Telescope" (Willmann-Bell, 1984). The book
   includes a program to perform these calculations, but it is
   flawed by its frequent failure to find the correct "reference
   parabola" (a necessary step to getting the wavefront error).
   The reference parabola is surprisingly difficult to determine
   in software; this program does it correctly.
2) COC method originated by Dick Suiter, and described in Telescope
   Making #32. Suiter developed this method to stay out of the
   reference parabola thicket. It produces results basically equivalent
   to Texereau, and may be a bit more accurate.
2) Millies-Lacrois tolerance graph. Described in Sky and Telescope
   February, 1976. It does not provide a wavefront error value, but
   is generally considered a useful supplementary method.

The program is menu driven, and should be easy for anyone familiar
with the general techniques to use. Once the program has computed
the data sheet values, it can then output a pair of graphs, one of 
the surface profile, and the other the Millies-Lacrois envelope
chart. Also, the data sheet is saved in a file, so that it can be 
printed outside the program.

Some less obvious program features:

- The mirror parameters can be saved in a file. The program can
  then read this file after a later figuring session, in lieu of
  typing them again from the keyboard.

- The units of measure can be changed from the default of inches
  to either millimeters or centimeters.

- When multiple sets of readings are taken, the program computes
  the wavefront error from each set of readings, as well as for
  the average of the readings. This gives the user some indication
  of how repeatable and reliable his/her measurements are.
  A more sophisticated way is to use the Monte Carlo simulation
  option of the program. The program computes the mean and standard
  deviation of the readings taken at each zone. It then generates 
  random sets of readings that are normally distributed with the same 
  mean and standard deviation, and gets the wavefront error for each
  set. A histogram is then produced that shows how the wavefront
  values would be spread out. If effect the program says: if you
  made, say 5000, more sets of readings, this is how your wavefront
  results would be spread out. 

- The y-axis units of the surface contour graph is wavelengths;
  Texereau uses microinches. 

- Some users may want a printout of the graphs. Here's one way to
  do this:
  + Start the program from MS Windows. If the display is in full
    screen mode, change to a window (press Alt-Enter).
  + With the graph displayed, select Edit/Mark from the control
    menu (box in upper-left).
  + Drag the mouse to select the entire graph.
  + Select Edit/Copy from the control menu. This copies the graph to
    the clipboard.
  + Back in Windows, start Paintbrush, and Edit/Paste the image.
  + Use File/Print to send it to the printer.
  Obviously the graphs can also be pasted into other programs, such 
  as MS Word.

- Normally, of course, the program computes the surface error relative
  to a parabola. However, if it is invoked as "tex -s", (s for sphere)
  the error is relative to a spherical surface. Some may find this useful
  in the polishing just before parabolizing.

- Tex can compute the dimensions of a standard Couder mask,
  given the mirror diameter and the number of zones. This
  can be done with pencil and paper, but why bother?

Tex is written in ANSI C, and the source is included. However, the 
graphics would make compiling it problematic with compilers other 
than Borland C. The executable uses the floating point hardware if
present. The graphs will work with VGA and EGA graphics hardware,
but if you only have CGA, all bets are off.

If this software is distributed, it is requested that the source,
executable, and this readme file be included.

We welcome user's comments.

VERSION HISTORY

version 1.0 first release. Basic Texereau algorithm
version 2.0  first release of graphics version
version 2.1  6-27-95
        added centimeters, millimeters, or inches menu selection
        added y label to surface and ML graphs.
        corrected bugs in Focus method of COC search.
        corrected bug in display of COC constant.
        Thickened the data line in surface and ML graphs.
version 2.2 11/11/95 fixed bug that sometimes occured when readings on
	2 diameters was entered.
version 2.3 1/22/96 Add "-s" option so that errors can be computed
	relative to a sphere instead of a parabola.

11/95
Larry Phillips  rglwp@attme.cnet.att.com
Dale Eason      deason@NILE.STPAUL.NCR.COM
