Hi Kim, In our free body diagram we can't forget that the textbook also obeyed all the laws of physics. <g> The big old C band ( 10 GHz) dishes were setup to move along the celestial equator (dec 0 degrees) to pickup geostationary satellites. I suspect that the off axis noise (i.e. sidelobes and all that stuff) from the cylindrical parabaloid would give you more problems than a parabolic dish with a standard feedhorn and low-noise block (LNB). As far as the dinosaur dishes - that is what I am using. I took off the standard feed horn, LNB, etc. and replaced it with a feedhorn, low-noise amplifier (LNA), and very low loss coax that is usable at 1.4 GHz instead of 10 GHz. If you are interested, there are a couple of articles that I wrote for the OAS Star Diagonal a few years ago concerning my setup. Dr. Palen from Weber State has them archived at the following URLs: http://departments.weber.edu/physics/palen/OAS/Newsletter/Mar01.htm http://departments.weber.edu/physics/palen/OAS/Newsletter/Apr01.htm So, get that radio telescope project back out and get back to work on it - its a lot of fun! Clear skies, Dale. ________________________________ From: utah-astronomy-bounces+dale.hooper=sdl.usu.edu@mailman.xmission.com on behalf of Kim Hyatt Sent: Thu 9/8/2005 9:52 PM To: Utah Astronomy Subject: Re: [Utah-astronomy] cylindrical parabolic antenna [was: amateurradioastronomy ] Dale: Yeah, I think that you're basically right on all points, but I'm relying on 35-year-old memories from my AP physics textbook, the one that went end-over-end down the median of I-15 with me and my '65 VW Beetle when we tried to defy Newton's 2nd Law of Motion one very cold December morning in 1971. Or was it the 1st Law? I've always been grateful to UDOT for modifying the design of the steel guardrails the previous summer so that I vaulted over the railing rather than getting impaled on it when our respective molecules collided. But I digress... In the days of the six- or seven-foot satellite TV dishes I wondered why it wouldn't work to build a cylindrical parabaloid (again, simplicity and cost) rather than pay the hundreds or thousands that the dish makers were charging. And, do those dishes, that I assume are now dinosaurs, have any use in amateur radio astronomy, or are they "tuned" (wrong terminology?) to the wrong wavelength? Do you, Dale, or does anyone else know the answers? I don't have enough hobbies and I've been thinking about building that aborted radio telescope that I never completed in high school. ;-) Maybe I'll even try to locate my old Beetle and restore it, too. The physics text could even still be inside. Who knows, I might even find that old stash of...never mind. Kim