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Originally Posted by avandonk
I could be out of line here but do you planetary guys take into account the size of the Airy Disk. At f32 it is 22 micron and at f64 43 micron for green light even with perfect optics. It is even worse for red.
Just wondering.
Bert
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Hi Bert, my feeling on this is that there's no problem with oversampling the image as long as there is sufficient light for the camera to keep the signal to noise at a reasonable level.
Shorter exposures, and larger sampling, make it easier to recover the final image in the presence of unpredictable turbulence and added noise from the camera etc.
Also, the airy disk for a star is maybe not quite the same thing as the combination of airy disks from a planet - in the latter case you have many overlapping airy disks, and so there will be transitions of colour and light/dark between these disks that are smaller than the disks themselves. Sampling at a larger size than the disk allows you to detect these edges more clearly.
If you think about what you see on a planetary image live in the eyepiece, you don't see a collection of circular airy disks - if you did then the planet might look like a collection of sharply defined circular spots. Instead you see the sum of all the disks from an infinite number of points across the image, and so there must be detectable features that are smaller than the individual disks. Not resolved features, but just detected features.
On Jupiter, say, this may allow you to detect the presence of a tiny dark spot corresponding to a storm in the polar region that would not otherwise be seen.
regards, Bird