Makes a copy of the masterdark and index file in the calibration library
This primitive is suitable for optical imaging instruments.
Processing only occurs for dark frames, and when the steering header MAKE_DARK is true.
"
dark_<instrument>_<UT
night>_bin<Xbin>x<Ybin>"
where <instrument>
is the LCOGT instrument identifier and
<Xbin>,
<Ybin>
are the binning factors in X and Y.