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Old 22-11-2013, 04:56 PM
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Peter Ward
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Peter Ward is offline
Join Date: Dec 2007
Location: The Shire
Posts: 7,103
Originally Posted by Shiraz View Post
But for DSO imaging with apertures above about 6-8 inches, it probably does not matter much.....
I beg to differ.

Hubble pre and post servicing is a good example.

Throwing some light into the first or second diffraction rings I find to be rather moot.

"Oh dear my MTF is less than perfect APO refractor of the same aperture!"

All I can say is: lots of luck with your 12-14-16 inch refractor

Fact of the matter is: a high quality optic will give you sublime focus, and with some exotic designs this will extend across an entire field (eg KAF 16803).

This is not the same is scattering incoming starlight all over the aperture and/or simply not being able to focus...which is what poor optics do.
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