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24 Inch F 3.2 Schmidt Newtonian

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Posted by Rick Crockett on October 21, 2006 06:47:00 UTC

Same disclaimer as above, I can't see any replies.

But If you have decided on the route, I am not sure why you would need a Ray Trace.

BK-7 is not PYREX and it will flow under stress. I think for a corrector, you will find a 1/4" too then for 24" in diameter. Then are you going to hang a 7lb. diagonal on it as well???

Generally when the corrector is at FP instead of RoC, it is advised to share the correctoin between both sides. To deal with a thin corrector it is possible to make a conformal back stop. It would be parabolic for figuring the first side. I am not sure when doing the second side, that the glass is thick enough to not to require another one that I guess would be spherical.

Maybe you might want to think about just using the BK-7 as a window and figure the mirror as a paraboloid instead of a sphere, then use a coma corrector.

Otherwise you have to deal with a spherical focal plane. The curve is substantial in a Schmidt-Newtonian as fast as you are planning.
A field flatter will be need for visual and CCD work. Film can be pulled into a concave by way of a vaccumm plate.

I wish you luck on this but I wonder how much experience you have. Somehow I feel you would be far happier with a 24" standard Newt. of maybe f:4- f:5 I have a 22" f:5 I made 27 years ago and it is peaches... Especially with a 40mm eyepiece and a coma corrector.

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