TEX - MIRROR NUMBER CRUNCHING MADE EASY Version 3.2b Tex is a 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 two 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) 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. Other features of the program include: 1) Can handle inches, millimeters, or centimeters. 2) Can save mirror constants, so they don't have to be entered by hand after each test session. 3) Producing a file suitable for use by the Aperture program (available from Willman-Bell). 4) Computing the mask opening boundaries for a couder mask. Can print out the resulting mask (see note below). 5) Provides a "monte carlo" readings simulator, which can be used to determine the confidence of your data. NOTE: printing is supported for PostScript only. For systems without a PostScript printer/viewer, there is a free one called ghostscript (or ghostview for the viewer) for just about any computer/printer you can imagine (see http://www.cs.wisc.edu/~ghost/ for information). Tex has been compiled and run on the following OS's: - MS-DOS - Linux 2.0 (intel platform, ELF format) - HP-UX 9.0 - Solaris 2.4 and 2.5.1 (sparc platform) - Apple Macintosh Note that on UNIX platforms, the preferred name is texereau, not tex, as there already is a UNIX program called tex (Knuth's TeX typesetting program). If you compile the source code for another OS/platform, please send the authors the binary, and we'll be happy to post it (space permitting). 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. This must be done BEFORE entering or reading in any data. All data must be entered in the same units. - 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 from DOS: + 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. Non-DOS users will already have the graphs as PostScript files, and can simply print the files (either on a PostScript printer or using a PostScript emulator, like ghostscript - see above). - 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 are displayed from within the program only for MS-DOS users On other platforms, the graphics are converted to PostScript and saved in a file, which can be printed or viewed. The DOS executable uses the floating point hardware if present, and will work with VGA and EGA graphics hardware, (if you have CGA, all bets are off). If this software is (re)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. version 3.0 12/1/97 fixed several bugs, added cross-platform support as well as PostScript graphics support, added ability to print a couder mask. version 3.1 12/9/97 fixed bug in calculation of surface error. version 3.2 12/29/97 REALLY fixed bug in calculation of surface error. version 3.2a 1/20/98 Added support for Macintosh platform version 3.2b 1/22/98 Fixed file input of tester type for DOS platform, 1/98 Michael Lindner mikel@att.com http://home.att.net/~mikel Larry Phillips lwphillips@lucent.com Dale Eason deason@NILE.STPAUL.NCR.COM