The MacRonchi program

MacRonchi 1.2

By Gert Jan Verhoog, october 14, 1998



This is a freeware program that is useful for Amateur Telescope Makers (ATMs) that are in the process of making a telescope mirror. It shows what the reflection of a ronchi grating should look like at certain distances from the radius of curvature. It is based on the ronchi program (version 3/18/97) by Mel Bartels. For more info, visit his page on the ronchi test. Also check out my page on interpretating ronchi shadows.

MacRonchi Screen shot

System Requirements

The MacRonchi program should run on all Macs that have Colour Quickdraw (almost any mac). There's a 68K and a PPC native version. If you have a Powermac, use the PPC version, it should be a lot faster. The 68K executable is around 270K in size, the PPC version is around 350K. The program requires a minimum of 512K free RAM to run (1024K preferred). To unpack the distribution, you need something like stuffit expander.

When MacOS X is released, there will be a version that runs natively on Mac OS X.

Version History

1.2Fixed a bug that caused the inside-RoC images to be drawn incorrectly. Thanks to Robert Duvall for pointing this out to me. Also added an option for selecting a fixed or moving light source, rearranged the items in the window a bit to look nicer, and changed the bitdepth of the offscreen graphics area to 2 so the program consumes a lot less memory.
1.1changed algorithm to plot all points, instead of picking points at random - turns out to be almost as fast, and looks a lot better.
1.0initial release.


Although I don't think this software will destroy your computer will have any negative effects on your mirror, and I'm reasonably sure the ronchigrams produced by the MacRonchi program are correct, I can't guarantee that it will work on your particular machine or that the results are accurate. I cannot be held responsible for any damage, direct or indirect, that is caused by using this software.

Notes and Feedback

I am unable to continue development of this version of MacRonchi, that runs on the 'classic' MacOS (up until MacOS 9.x). However, I'm working on a set of ATM tools that will run on Mac OS X, including a new version of MacRonchi and a tool to do Foucault data reduction. I'd really like your feedback, so I can incorporate improvements in the Mac OS X version of MacRonchi. Please send e-mail to

Conditions of use

This software is freeware, download it, give it to fellow atm's, and do what you like with it, under the following two conditions:

  • You are not allowed to sell MacRonchi or make money with it in any other way.
  • You're not allowed to redistribute modified versions.


Download the software by clicking the appropriate link.

© 2000 by Gert Jan Verhoog