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SBIG CFW-9
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vignetting (such as a variation in the sky background level) then you
should also take flat field images and flat field correct your primary
images using CCDOPS. Whether you need to take different flat field
images for each primary color or not will depend on how different
the vignetting pattern is for the different primary images. Typically
a single flat field image will suffice.
Color Image Processing
A complete description of color processing is beyond the scope
of this manual. A complete description and step-by-step
instructions may be found in the CCDSoftV5 manual. Different
software packages may handle the combining differently, but in
general, you register or co-align the primary color images. You
select the Red image from the set of three primary images you want
to register and the software then loads and displays it. In that image
you select a reference star (or pixel) and this reference star (or pixel)
is used to register the Red, Green and Blue images to one another.
Once the images have been registered, they are merged together to
form a tri-color image and minor adjustments are made to achieve
color balance.
Third party software packages such as Maxim DL and Adobe
Photoshop are popular programs for combining the three primary
images. While these packages tend to be expensive, often times you
can find last year's versions at a sharp discount and they really are
powerful image processing packages producing the most
professional results.
Note: In most cases, before doing a color merge, attempt to have
all RGB images saved with a similar range or contrast setting. This
will make the initial result closer to what you desire.
