Re: [ATM] Re: 25" mirror possibilities

["Bob May" <bobmay@nethere.com>]

I'll note that any lens placed near the mirror will necessarily have the
light pass through it twice and that will be a problem.  The diameter of the
beam will be different each way through unless it is right on the mirror,
making it practically a Mangin mirror.
I'll note that the reason why the Schmidt and other correctors work so well
is that they make a correction to the wavefront of the light in such a
fashion as to make the light, when it is finally focused by the system, act
like it was reflected by a parabolic surface on the parabolic surface.  Part
of that process is that the corrector should really be placed at the proper
location so that the light path is perpendicular to the reflection angle for
that incoming angle.
Bob May
bobmay@nethere.com
http://nav.to/bobmay
http://bobmay.astronomy.net

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