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Re: CCD saturation [message #63022]

Sat, 25 October 2008 06:33

Wox
Messages: 184
Registered: August 2006

Senior Member

Marshall Perrin wrote:

> Shape detection is not the way to go here, versus detecting the level
> at which pixels saturate. There should be some characteristic number of
> counts per pixel below which you know data is not saturated.

Yes, but this only works for the inner part of a saturated spot +
streaks. The edges don't have a value of 65535 (it's a 16bit CCD
camera) and can in fact have a lower value than non-saturated spots
which I want to preserve. That's why I could only think of shape
detection to differ streaks from spots. However I'm not really able to
do that. I usually remove a lot of non-saturated spots too.

The problem I want to solve is illustrated here (X-ray Powder
Diffraction): http://www.datasqueezesoftware.com/screenbig.jpg
You see the so-called Debye rings in the image in the background and
the azimuthally integrated pattern in the front. Usually you don't see
this nice rings, but alot of spots forming a ring (or more rings).
Imagine azimuthally integrating this when some spots are saturated
with streaking. You don't end up with nice Gaussian peaks like in the
figure, but some strange ..euhm.. things... that may look like peaks.
If I could just detect the streaks and set these pixels to zero, I
solved the problem.

Since there are alot of astronomers here, I would think they also have
similar problems to solve, only their spots are not scattered X-ray
beams but stars :-).

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[Message index]

		Re: CCD saturation By: Wox on Sat, 25 October 2008 06:33
		Re: CCD saturation By: Marshall Perrin on Fri, 24 October 2008 15:23
		Re: CCD saturation By: JMB on Mon, 27 October 2008 09:47
		Re: CCD saturation By: pgrigis on Mon, 27 October 2008 06:27

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