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Old 18-01-2020, 01:25 PM
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Outcast (Carlton)
Always gonna be a NOOB...

Outcast is offline
Join Date: Oct 2008
Location: Cairns, Qld
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Originally Posted by glend View Post
Well a couple of things: an RC is more of an imaging scope, it is faster at f8, but has a larger central obstruction (say 40%), the hyperbolic mirror set is designed to be coma free (well third order in theory, and free of spherical aberation).
The Cassegrain has a smaller central obstruction ( say 30%), and is slower at f12 (ie longer focal length, and not as concerned with coma at the edges.
The Cassegrain is the original folded design which the RC grew out of, in a sense.
That's my take on them, one RC is an astrograph design and the pure Cassegrain is visual mainly but can be used for planetary imaging.
Originally Posted by Saturnine View Post
In basic terms the Classical Cassegrain has a parabolic primary and hyperbolic secondary mirrors and is more suited for higher magnifications. The Ritchey Chretien design is a hyperbolic primary and hyperbolic secondary mirror. The RC design is chosen to eliminate coma over a wider field, to make it more useful for astrophotography.
Thankyou gentlemen, I learned something more about optics..

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