Archived from:

Telescope Design Software

WINSPOT V0.95d by David Stevick - now launches by association under Windows XP.

Based on the DOS version of the program, Winspot is easier to use with more menu options, and takes advantage of standard Windows printer support. Page printouts of your designs are a breeze.

Winspot allows animation of the spot diagrams through focus (real time focusing). The focal surface can be tilted, and curved, in real time also to examine how the light behaves as it impinges the focal surface. A help file is included and contains a mini-tutorial on tilted-component design.

Thanks to José Sasian and Jonathan Bokelman for contributing algorithms to Winspot.

TCT's by José Sasian

José Sasian's doctoral thesis was on Imagery of the Bilateral Symmetrical Optical System (TCTs) and as such he is highly qualified in the field. His program is slick and calculates many parameters which gives the program immense capabilities. It will trace Schiefs as well as Yolos which have toroidal surfaces. It can also apply comatic deformations to mirrors, although making such surfaces may be out of the amateur's reach. A more advanced feature is its ability to vary parameters to optimize aberrations.

What I like best is that aberrations are expressed in terms of the Airy disk. A value less than 1 indicates the Rayleigh criterion has been satisfied. Values over 1 show excessive aberration.

Several graphics plots make the program most useful. It will draw the system layout, show the focal surfaces, and plot spot diagrams. A variety of tabulation screens reveal everything you could want to know about the design. And of course, you can design a plain Newtonian if you want.

SPOTPLOT version 2.0 by David Stevick.

David Stevick's DOS program displays aberrations in the manner employed by A.E.Conrady and later modified slightly by R.Kingslake. The program provides results in numerical form or as spot diagrams. Highly enlarged, random plots of the central image show the light distribution. A menu is provided for easy use of the program and selection of files. It will trace both symmetric and toroidal surfaces. The program does not require you have a mental picture of the design and which way a mirror curves or which way a ray is traveling. If you have gotten weird results with other programs because you entered a positive air space when it should have been negative you will appreciate this feature.

This will likely be the last DOS release of Spotplot. It does contain some features not yet present in the Windows version. The current compile is larger than the version released as a beta, but was done to allow users of 386-SX's to be able to run the software. It's not otherwise significantly different. A pif and icon are provided so that it can be launched from Windows.

HERDESN by James Vogh.

James Vogh has written a Herrig Telescope design program which will run on either a PC or a Mac. Required parameters are only the desired aperture and focal ratio. Design files are created for loading by Tct's, Spotplot, or Winspot, and a companion program, HERMIR, uses results from either Tct's or Winspot to specify required mirror diameters.

This software is pure, straight, interpreted BASIC. That's why it can run on either platform. (You do remember how to use QBasic don't you :)? Oops forgot, that's a native part of DOS. Let's see, type qbasic, load herdesn.bas, run the program. Hey, that wasn't bad!

E-mail Jim - granny at

Original SPOTPLOT version 1.0

You may want this package if the following applies. You wish to read the manual, you have a friend running an XT or 286, or you want access to the source code. The original program did not draw the system schematically, nor did it handle toroidal surfaces. But it runs on anything, even a Hercules monitor, and the raytracing equations are still valid and included in the source.

Back to Weird Telescopes

Author: David Stevick
[Weird Telescopes Page]

Curator: Hartmut Frommert [contact]
[Schiefspiegler Home] [SEDS]