>"wonky"?? Is that a technical term <g>.
>My limited understanding of CCD devices tells me the primary difference
>between astronomical CCD cameras and "consumer" CCD's is the astro ones are
>electronically cooled to very low temperatures to increase sensitivity and
>reduce noise. While I'm positive Lee can explain more accurately, with an
>astro CCD one takes two exposures to get a picture - a "dark frame" and the
>image itself. The dark frame is all black, except for the noise patterns
>for that CCD. The dark frame values are then subtracted from the image
>values to produce the first generation image. I say first generation
>because there is usually subsequent manipulation after the image is captured
>and that manipulation depends entirely on what one's objectives are.
>
>If you have image manipulation software (photoshop, gimp, ???) that can
>register and subtract, take a dark frame and save it for reference. Then
>register it with an image, subtract and save. You can then further modify
>the resultant image for crop, color balance, etc. I believe you will see
>the artifact disappear.
>
>John P
>______________________________________
Or maybe what would be good is for the camera to have a feature where
you can store a dark frame yourself and let the camera electronically
subtract the noise. But it probably depends on exposure time and
is not so obvious for "normal" expose times -- only long duration
exposures.
Mark H.
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