Re: Off-Axis (Zero Obstruction) Reflector Telescopes
From: Jon Isaacs (jonisaacs_at_aol.com)
Date: 10/03/04
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Date: 03 Oct 2004 18:30:15 GMT
>Would a 16 inch Newtonian reflector with a 6 inch off-axis
>aperture stop mask be a good choice for maximum magnification
>lunar viewing in situations where seeing is ideal?
>
If the seeing is "ideal", then a 16 incher with an aperture mask would be a
good choice as long as the mask were not used.... : <G> (A Semi-Grin)
As we all know, we did go through this discussion a while back...
My understanding of the potential optical advantages of the OA Newt over a
larger Newt with an aperture mask"
1. Thermal issues, an OA Newt can have a smaller mirror which should reach
equilibrium more quickly and the OTA can be larger allowing for better cooling
and few issues with tube currents.
2. A fully illuminated FOV. Since the focuser can be on the opposite side of
the diagonal from the primary mirror, there is no difficulty fully illuminating
the FOV. It also may place less strict tolerances on the quality of the
secondary mirror.
There are other factors such as increased Coma over standard Newtonian of equal
focal ratio, (ie ~F10), the obvious one of loss of light gathering over the
unmasked large Newt, the size issue and length issues.
jon
Jon Isaacs
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