QHYCCD QHY8L User Manual
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DARK
DARK image refers to the image in which exposure time is the same as the light
images. You need to avoid any light entering into CCD when you are shooting.
Therefore, you need to cover the lens cap of camera. The exposure time is set to be
the same with formal shooting time, and then use the low speed, 1*1 shooting mode to
shoot 10~50 DARK images. Save them, and then use stack software to get a DARK
master image, and save this image.
FLAT
FLAT images can be used to rectify the problem of a lighter center light but darker
edges caused by vignetting in the optical system. All optical systems exhibit vignetting
to some degree. The shooting method for flat field images is the following: Point the
telescope at a uniform light source, such as clouds, or make some type of uniform light
source using a suitable diffuser. Set an appropriate exposure time, and start to shoot.
You should shoot 10-50FLAT images. Save them, and then use stack software to get a
FLAT master, and save this image.
•
It is best to take FLAT images immediately before shooting or after shooting.
Otherwise the position of dust on CCD surface may be moved when you
dismount your equipment.
•
To set an appropriate exposure time, remember that the result should be 30% or
so of the maximum dynamic range, which means that the FLAT image’s white
pixel value should be 20000-30000.
Dark Flat
Dark Flat image is a Dark image in which shooting parameters are the same as with
FLAT images. If you wish to include these images, you need to cover the lens cap of
camera, set low readout speed, set the binning model to 1*1, then shoot 10~50 Dark
Flat images. Save them, and then use stack software to get a Dark flat master image.
Then save this image.
Stacking and Combining
Registration, quality selection, and stacking of all images is easily managed by the free
software package Deep Sky Stacker,
After you combine and stack your images, the result can be further processed by
Photoshop, PixInsight, or other programs.
The table on the following page summarizes the calibration images: