InvRon - Inverse Ronchi Grating Program

Ordinary Ronchi gratings have straight lines. When used to test non-spherical mirrors, they produce curved shadows. An inverse Ronchi grating has curved lines, calculated so that, when used to test a non-spherical mirror, they will produce straight shadows.

Grating pattern on the left is for an 8 inch f/7 paraboloial mirror. For use, the pattern would be reduced on film to 0.0287 inch diameter.

More about Inverse Ronchi Gratings Contains a complete Windows setup package for InvRon. Unzip this file into a convenient (preferrably empty) folder and run Setup.exe. This is version 1.1.13 The .zip file is 1,787,011 bytes long and contains 18 files.

InvRon uses a freeware printer control called SwiftPrint. SwiftPrint in turn uses subroutines from the Microsoft Foundation Classes library version 4.2 (MFC). Many programs use MFC subroutines, however, at least as of Windows 98, the MFC routines are not usually included with a normal Windows installation. Your system may already have them as a result of installing another program. If your system does not have them, you will see errors when you try to install InvRon. The errors will refer to swiftprint.ocx

You can download the necessary files from various sites. Here are two:

Once you have installed the MFC files, you can delete the .zip files and the setup files.

With the MFC files installed, rerun the InvRon Setup.exe to get SwiftPrint properly installed.

The help file for InvRon is in HTML rather than the standard Windows help file format. It will open in your default browser. The help file uses HTML frames to display a table of contents in one part of the screen and the text in another.

The help file actually consists of three HTML files: one for the frameset, one for the table of contents and one for the text. The help HTML files can be downloaded separately as After unzipping, point your browser at InvRonHelpFrames.htm

Most browsers display frames well, however if yours does not, or if you just don't like frames you may download this file

The frames version of the help file actually consists of three files: InvRonHelpFrames.htm, InvRonHelpTOC.htm and InvRonHelpText.htm Delete or rename them and unzip InvRonHelpNoFrames.htm from into the same directory as InvRon.exe. InvRonHelpNoFrames.htm will then function as the help file.

You can view the Readme.txt file and the InvRon Help file by clicking these links.

InvRon Has Maximize Button Disabled

By design, InvRon has the maximixe button at the top right corner of each window disabled. This is because the form elements do not change size when you maximize. Maximizing does not do anything useful.

Auf Deutsch!

Martin Trittlevitz has been testing InvRon and using inverse gratings to test mirrors. Martin has written a web page in German describing both the program and the test. Danke Martin!

Martin's web page is at

Martin's home page, with other telescope making information is at

InvRon is licensed under the GNU General Public License. This obligates me to make the source code available. I am not quite ready to post it here. The code still needs some cleanup. Eventually I will post it here, or wherever InvRon's web home is at that time. In the meantime, If you really want to see the code, warts and all, please e-mail me.

If you have problems, questions or suggestions, please contact me at

Copyright © 2001, 2002 Mark D. Holm

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