Not an optics expert, but have come up with an Excel spread sheet for a simple three lens scope optical design, similar to a Unertl or Fecker scope.

Input objective lens diameter, the three lens focal lengths, and the desired magnification. Output is lens location, overall length, exit pupil, eye relief and field of view.

Seems to work. Built one pretty good scope using it and shows the FOV screw-up on another one. Does not eliminate testing due to various tolerances, but is a good starting place.

Because the Forum does not handle Excel, you will have to E-mail for a copy. 
( chasdeats at yahoo dot com ) or my profile.   Will attach a copy to the reply. Almost as much fun as a computer game to get what you want and sometimes you can’t with three lenses.
Chuck

Chuck sent his program to me and I can highly recommend it. It's easy to understand and in turn, makes it very easy to build one.

I hope to try assimbling one within the next two weeks.

Frank

Here is a better link to get lens's for a scope build. I have used as well as talked to people from Edmonds and they are very nice and can be very helpful
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Sam