RATDATA is an Excel Workbook that helps you analyze the readings from a Foucault tester with a five zone Couder Mask. The worksheets display the data graphically and in table format. It is modeled after the ideas of Jean Texereau, Richard Berry, and others. The user simply enters the data and RATDATA quickly shows what that step has accomplished. The user may also print a single sheet report to keep in the figuring notebook.

Because it uses the Windows/Excel interface, the program is easily adapted to individual tastes and needs.

This workbook contains a "Readme" sheet of instructions and two other worksheets. "Working Data" is for day to day figuring. "Two Axes" follows the same program logic, but allows comparison of data to check for astigmatism, or to see how the work has changed the figure between testing sessions. Return to top.

RATDATA is the result of more than a year’s work by various members of the Riverside Astronomical Telescopemakers. On Thursday evenings, we meet to discuss, argue, and gossip about mirror-making—and of course, to make telescopes while we are doing so. A common topic is how to use Foucault, Ronchi, and star testing to make better mirrors. RATs believe a complete polish, a smooth donut, an excellent edge, and lack of significant astigmatism are what are needed in a finished mirror. In our discussions, we often talk of Texereau, Berry, Kestner, Bartels, Millies-Lacroix, and how they represent the surfaces of mirrors from the results of Foucault tests.

Much of their work was done before computers were commonplace. In the early years of the PC, extraordinary efforts were made to implement computer analysis of Foucault test data. "TEX", "Admir", and other DOS-era programs have done a good job illustrating the data. But DOS programs are showing their age. They were written before the Graphical User Interface (GUI) became popular, and do not offer the advantages of the Windows interface. Some require restarting from the beginning if a mistake is made at any point during data entry. Printing requires a multi-step operation and an additional graphics program. There are few options for adapting them to individual needs, preferences, or tastes. Finally, one needs a collection of these programs. Each has a different interface and multiple menus, and requires re-entering the data to get the job done.

To address these issues, we have written an Excel Spreadsheet that updates and combines the capabilities of the DOS-era programs, while providing the advantages of the GUI. Color for emphasis, point and click, easy data entry, resizing, adding or deleting graphs, running "what if..." scenarios, and all the functions of a spreadsheet are available in RATDATA. Directions and documentation pop-up as needed. Return to top.

With RATDATA, one can enter a set of readings, run the calculations, summarize the data, determine the overall wave rating, and draw two tables and three graphs representing the results in twenty five keystrokes and a mouse click—and the data alone takes up twenty of those keystrokes. Return to top.

A final word should be said about "wave ratings". RATDATA uses the wave rating as a useful measure of progress during figuring. It is not, in itself, the final word on the quality of a figure. "Wave" is a word with many possible meanings in this context. In RATDATA, "1/8 wave" is meant to reflect the Raleigh criterion for a diffraction-limited mirror. This criterion specifies that if the actual wavefront, after reflection, differs from perfection by less than ¼ wavelength of the color of light that the eye is most sensitive (560nm), then the image formed can appear essentially perfect. We emphasize the words "after reflection", as this means the mirror surface error must be no greater than 1/8 wave. The reflection doubles the surface error. This, of course is an ideal situation, and assumes there are no other contributors to image deformation in the light path. (see Suiter, H. R., Star Testing Astronomical Telescopes for the definitive work on image aberration). The "1/8 wave" confidence bands plotted in RATDATA are meant as a good approximation of the Raleigh criterion.Return to top.

We hope you find this workbook useful. If you have any ideas on additions, alterations, or improvements, please contact us. Return to top.