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Old 12-12-2011, 05:51 PM
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irwjager (Ivo)
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Quote:
Originally Posted by Merlin66 View Post
IVO,
You need to read the document I attached to the last message...
I take into account the f ratio and the camera pixel size in the calculations...
The enlarged saturated star images appear to exceed the diameter of the Airy rings..
There is no diameter of the Airy rings. These rings extend throughout the image - e.g. all wells on the CCD (or film) get a tiny bit of light.

EDIT: I see in your document you define the 'Airy disk diameter' as 2.44 x Lambda x f ratio. This formula is an approximation of the position of the first minimum, but many, many minima (and rings) follow. The disk that you define only contains 83.3% of all the light, with the rest being spread out over an increasingly large area away from the star, concentrated in further rings. Expose this area long enough and it will start showing up, gradually 'growing' the stars until the whole image saturates.

Quote:
Re Hubble - this would then infer that the brightest star image recorded will always been no larger than the extended Airy disk...is that really the case???
Not sure what you're saying here, but rest assured that an incredibly bright star, which would be incredibly far away (e.g. for all intents and purposes a point light) can easily swamp Hubble's CCD wells with a long enough exposure.

Last edited by irwjager; 12-12-2011 at 06:07 PM.
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