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Testing An Hyperboloid Convex

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Posted by Luis on June 18, 2000 23:47:04 UTC

How to test an hyperboloid convex for a Classic Cassegrain or a Ritchey Chretien secondary?

I`ve been reading some techniques in Texereau`s book "How to make a telescope" but none of them makes me sure of the better method..

Only the Fizzeau device test seems to be quite exact, which consists in building a concave and a convex mirror at the same time, same focal length, and while getting the right curve at the foucault for the concave, compare both mirrors at the Fizzeau searching for straight newton lines.

I guess this method will be quite hard to succeed, as keeping both mirrors with the exact same focal distance while polishing is very difficult.

Any other method out of auto collimating? (mounting primary and secondary on the tube and see how it looks like).

Thanks

Lam.

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