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Re: Ritchey-Chretien

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Posted by Robert May on May 1, 1999 05:24:53 UTC

If you're trying to build something that will fit into your apartment best, the Newt. is hard to beat. Do a 10" with the techniques that the huge scopes are made with and you will be able to put the scope into a small suitcase sized package with the exception of the poles. The R-C is a difficult beastie to build for a firsttimer as the secondary is a convex hyperboloid which requires auxiallary optics to test (the Hindle sphere) or at least a flat the size of the primary (doing the double pass test) and both of the optics are pretty critical in thier radiuses. After you are able to grind and polish to a close radius and test the optics of strange things, go for a R-C as it is a nice scope. It is very easy to go overboard on getting accurcacy with your desires. A scope with 1/8 wavefront error will do for almost any chore that you want it to do. You might look at Ross Correctors for a newt if you want to cut down on the coma that happens with a short FL scope, but a 6"F10 is a pretty comafree instrument. In other words, a R-C is going to be big because you don't want to tear it apart for moving and storage while a Newt will easily allow for such. I know this isn't quite what you want to hear but it may be the best for a first scope. Grinding a mirror is easy and polishing isn't too difficult with the testing that is needed to be done. There are a number of sites out on the web that deal with the testers, etc. Go look for Foucault testers and other astronomy sites look for making mirrors/telescopes.

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