Quote:
Originally Posted by Merlin66
Bert,
""The reason bright stars are bigger than dim ones is that the very weak higher orders of the Bessel Function are saturating the sensor."
Not strictly true....
All star images will have the same FWHM...
What is happening is that the brighter star image becomes saturated and the dimmer images only record the brighter core "peak".
The PSF of the telescope can effectively destroy the neat Airy disk pattern.....
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Quite correct. I was considering perfect optics. Not the usual result that real optics give, a distorted image that can be approximated by a Gaussian function at best.
Central obstructions throw energy into the higher orders of the Bessel Function. Wavefront abberations just add to the Point Spread Function.
bert