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Originally Posted by alpal
So - you think that it 's all bragging rights then?
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I didn't say that.
What I did imply though was that people have been known to optimise one particular component of a system at great expense without doing a cost/benefit analysis with respect to how that impacts the performance of the system as a whole.
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I think if I searched the internet I'd find comparisons that would disprove your theory.
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Bearing in mind that the op was specifically asking about the impact of mirror quality in
newtonians it would be better to limit the comparison to images taken through newtonians, or at the very least, telescopes with apertures and focal ratios typical of newtonians.
A much easier way to see the impact of 1/3 wave on prime focus imaging would be to find someone with a newtonian of known quality and ask them to take a few images for you. With and without a 50% central obstruction (which could be circle cut out of cardboard) The diffraction effects of the larger central obstruction will be of similar properties and magnitude as 1/3 of SA.
There are many images on the net (even this forum) taken by instruments with 50% central obstruction that show no degradation of imaging performance by virtue of their central obstruction, so implicitly, 1/3 wave is good enough for such an instrument.