Quote:
Originally Posted by Wilso
Corrector plate vs spider veins?
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That is a bit complicated as it is like like comparing apples and oranges.
Have to compare transmissivity with obscuration and scatter with diffraction.
I don't know the exact numbers for the corrector plate, but the light loss due to spider vane obscuration will be 1.6% of the clear aperture, on top of the 7.4% caused by the central obscuration.
Light scatter by the two air/glass surfaces of the corrector plate is probably more detrimental than the diffraction effect of the spider vanes, considering how difficult it is to maintain the corrector in a pristine state free of any condensates.
Also most of the energy diffracted by the spider vanes falls outside of the planets image, thus not degrading the contrast on the planet.