Hi, Janis. Some books on astronomical optics, meaning the design of optics. Elementary but very useful: "Telescope Optics" by H. Rutten and M. van Venroiij. Published by Willmann-Bell. More advanced: "Practical Computer-Aided Lens Design" by G. H. Smith. Also published by Willmann-Bell. Very advanced: "Reflecting Telescope Optics" by R. N. Wilson. Published by Springer Verlag. If you're interested in refractors, you might like to look at my website, which is sort of medium advanced and includes apos and the Schupmann: http://alice.as.arizona.edu/~rogerc Hope this helps, Roger Ceragioli -- See message header for info on list archives or unsubscribing, and please send personal replies to the author, not the list.