Re: Photographic Size of a Star

On 28 Nov 2006 11:51:39 -0800, "atasselli@xxxxxxxxxxx"
<atasselli@xxxxxxxxxxx> wrote:

Actually, in real life we can see the Airy profile and the diffraction
pattern extends to infinity, exactly as a gaussian. IOW, it is not a
matter of a specific PSF but rather that the PSF extends to infinity,
with infinitely decreasing intensity.

It is rare to see the diffraction profile in images. You can capture it,
of course, with a deliberate fast exposure, but that isn't typical of
the vast majority of images. Once the exposure time is longer than a few
seconds, you lose the diffraction pattern to atmospheric turbulence, and
your purely Bessel PSF becomes approximately Gaussian. In either case,
of course, the size of the function is infinite, with the apparent
diameter determined by the noise floor.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
.

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