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Re: Saturation Improvements
Herbert R Johnson wrote:
>
> Not quite, Tom. For future reference, how do you determine when a star
> (a set of pixels) are "saturated"? This is not a silly question. As, over
> the course of time, you've adjusted the operation of the Mark IV, the
> value of "saturation" in terms of ADU counts has almost certainly changed.
> So I expect it would change in the future. COnsequently, anyone reviewing
> old data or new will need to know your definition of saturation - to determine
> it themselves on older images.
It's easy to know if a star is saturated. You don't need to know
much about the camera either. If you think of an image as a three
dimensional surface with stars as bumps the shape of the bump tells
you if the star is saturated. Normal stars have rounded tops while
saturated stars will have the tops clipped off making them look like
a plateau. A histogram will show you where the system saturates too.
Yes you can do photometry on saturated stars. You look at the shape
and size of the plateau and fit a curve to the bottom part of the
plateau then look to see where the peak would have been if it had
not been truncated. Likely a lot of messy details involved.
--
Chris Albertson home: chris@albertson-home.net
Redondo Beach, California work: calbertson@primeadvantage.com