QHYCCD QHY12 User Manual
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QHY10/12 CCD Chip Read-out Mode and
Image Calibration.
The QHY10/12 has a 2 channel/2 frame readout
CCD chip. There are several things you need to
pay attention to during the shooting and image
process.
The red and blue pixels are read from the left
channels. The green pixels are read from the
right side channels. The slight differences
between the two channels CCD creates slightly
different system gain and offsets between the two
channels. This causes bias frames that are
binned 1x1 to have a background color that is too
green or red.
You can generally correct this problem by using
BIAS frames or simply doing a custom white
balance.
1x1 binning images usually have some pixels of
color gradient at the beginning of each line. The
problem can be corrected through the BIAS field.
Some of your CCD Images may have a slight red to
green gradient from top to bottom. This is because
the pixel readout accumulated greater thermal noise
unevenly. (the thermal noise of pixel readout later is
bigger than the thermal noise of pixel which readout
earlier) Color gradient is the result of reverse
sequence of output pixels of the left and right
channel. This problem can be corrected through
BIAS fields.
QHY10/12 CCD chip uses a 2 phase readout mode.
The first phase is for the R and Gr pixels. The
second phase is for the Gb and B pixels. When the
end of the first exposure begins to readout - the
second field is still exposing. Normally this causes
the 2 exposure times to differ slightly. But in
QHY10/12 we use a technology to avoid this
happen.