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Re: Flatfield images for disk 6
Tom Droege wrote:
> 1) Horizontal banding.
> If one looks at the pattern of a small area one sees a dark band every 10
> or so horizontal lines. (I did not count them so I may be off - a lot.)
> This is probably due to feed through from the system clock. It should
> repeat from image to image, so it should be able to be subtracted out. I
> have tried, and it is not perfect, but it can be reduced by subtraction.
True enough you can subtract out the
effect on the flat field image put on an image filled with stars
subtraction will not work you need to divide.
You have to be right when you say these defects can
be corrected out. The flat field image IS the correction that must
be applied. Well, it is the multiplicative component of the correction
to be applied. The additive component is the dark frame.
Back to the bands: Would clock feed through be additive noise? This
banding is a variation in gain. Would the clock do that?
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