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How can we make a telescope at home?

Can I convert a newtonian telescope to a schmitt-casegrain ?

  • I have a 10" newtonian mirror in a semi-working home made telescope. Can I send the primary mirror to a lab and have them cut a hole in it to make a schmidt casegrain ? I know I need a special secondary concave mirror, but can they drill a hole in the primary mirror once its coated or do I have to pay for a new coating ?

  • Answer:

    I think you run a considerable risk of scratching the mirror when the hole is bored. Cassegrain mirrors are usually bored before grinding and polishing. Also, as stork5100 points out, the figure of a Newtonian mirror is wrong for a Schmidt-Cassegrain. But the bigger difference is that Cassegrain systems are generally based on a short focal ratio primary. You could build a classical Cassegrain based on your Newtonian mirror, but it would probably be f/30 or longer. The primary in a typical SCT is around f/2. You're also going to have to figure a way to make that corrector plate if you want a Schmidt-Cassegrain. (And the secondary is convex, not concave.)

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Sorry, but that won't work. Newtonian reflectors have a primary mirror with a parabolic curvature. Schmidt-Cassegrain's primary have a hyperbolic curvature. Even if you have a hole drilled into it, lights rays on your Newtonian will not converge correctly in a Schmidt-Cassegrain configuration. If you want to convert, you'll need a new set of mirrors. But, you'll be able to reuse the tube, mount, eye-pieces and and sighting scopes.

stork5100

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