These routines get an appropriate dark frame (dcdata) and its
index (dcindex) to match the images you are working with.
The routines find the full-frame dark image that is closest in
time and exposure level. The routine can interpolate between two
reference images to simulate the input exposure duration by using the
/INTERPOLATE option. It can be called with the index for a single image
by typing:
IDL> get_dc_image, index(3), dcindex, dcdata
where index(3) is the index of the image you are working with, or you can
pass a list array of indicies by typing:
IDL> get_dc_image, index, dcindex, dcdata, imap
For this case, imap is the same length as index and tells you which
image to use in dcdata for the corresponding index. For example,
if index is 10 elements long, and imap(8)=3, then you should use
dcdata(*,*,3) for the image that goes with index(8).
It is possible to extract the dark frames manually using a command
similar to the following example:
IDL> get_dc_image, xxx,dc_index, dc_data, times='1-sep-92 1:00', res=0, dpe=15
The SDC data files for the time period being calibrated must be in the
directory $DIR_SXT_SDC (and the SDW data files must be in
$DIR_SXT_SDW when calibrating images which were taken when the TEC is
off).