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Old 13-12-2011, 04:40 PM
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irwjager (Ivo)
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Join Date: Apr 2010
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Quote:
Originally Posted by Merlin66 View Post
http://www.lbto.org/LBT%20Website%20...e%20optics.htm
Go down to the bottom of the page....
1. Due to the nature of light a pinpoint star produces an Airy disk, surrounded by a Airy Pattern.
It's called diffraction. Light itself doesn't do anything by itself - it requires to encounter an aperture.
Quote:
2. All stars great and small produce the same linear diameter Airy disk for the same f ratio ie a 50mm f5 and a 500mm f5 produce the same sized Airy disk.
Stars don't produce an Airy disk, the Airy disk (re)produces the stars. The Airy Disk is a point spread function. A function light has to go through before it appears on the imaging plane.
Quote:
The limitations are not due to the Airy disk but the receptors ability to resolve and record the disk ( and the outlying pattern)
When you analyse a short exposure image, the star is still the Airy disk in diameter but with a much lower peak intensity. (See Star #4)
A brighter star (or more exposed star) has the same Airy disk diameter but a higher peak intensity (See Star #2)
Until you overexpose and the first few rings fill up (if you can even dissolve the rings at your particular magnification).

Like I said, I don't know what else I can say or do to explain better to you why stars seem to grow. You seem to have drawn your own (erroneous) conclusions, yet wonder why they don't fit reality. I think it's time I give up.

All the best,
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