Re:ATM Cassegrain as second telescope project.

[Richard Foulk <richard@skydive1.com>]

} > } I've thought about trying a cass system, since my first abortive
} > } attempt decades ago. Back then, I tried making the secondary out of a
} > } lens that had the approximate RC required.
} > }
} > } My biggest stumbling block was the thought of having to make one or
} > } more extra mirrors just to test the system.
} > } One secondary testing "method" I though about using was not to test
} > } the secondary at all before use. Give the primary as good a
} > } paraboloid as you can achieve, then star test the secondary, until
} > } the system performance is good.
} > }
} > } Another option would be to use the Dall method to test the secondary.
} > } It doesn't require making any extra test surfaces.
} > }
} > } Frank
} > } --
} > } Frank Henriquez  Programmer/Analyst  Jules Stein Eye Institute, UCLA
} > } frank@ucla.edu   http://www.bol.ucla.edu/~frank/index.htm
} >
} > I've been toying with the idea of grinding the concave inverse of
} > the secondary, to make it easier to test, and using that as a mold
} > for a carbon fiber mirror.
} >
} > Just a crazy idea ...
} >
} 
} If you are going to go through all of that trouble, why not just make a
} Gregorian instead?
} 
} Bill
} 

That's the point, it's not much trouble.  Or that's the hope.  Casting
composites is relatively quick and painless.  And cheap.  If you screw
it up you can do it again in an hour.  And composites have many other
advantages.


Richard