Description:
This primitive makes self flats from the current group, one for each distinct observation filter. For eacg
flat it uses a median to combine the frames pixel by pixel, and then divides the resultant image by its
mean form the flat field. The primitive files the resultant flat in its calibration index.
Notes:
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This primitive is suitable for infrared imaging instruments.
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Processing only occurs for object, sky, or calibration-lamp frames, and when the steering header
MAKE_FLAT is true.
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The list of filters present in the group is listed in an array stored by reference in the group user header
FILTER_LIST. If this is undefined, only a single flat is made for filter stored in the current Frame’s
user header ORAC_FILTER.
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There is special behaviour for a combined polarimetry flat (see "OUTPUT DATA"). The string "pol" in
the filter name is used to indicate polarimetry data.
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The flat is displayed.
Output Data
The flat field. It is called is
"flat_<filter>_<groupnumber>"
for the first cycle, and "flat_<filter>_<groupnumber>_c<cyclenumber>"
for subsequent cycles, where <groupnumber>
is the frame number of the group,
<filter>
is the filter name, and <cyclenumber>
is the cycle number derived from steering header CYCLE_NUMBER.
An exception is for polarimetric data, where the name becomes
flat_<filter>_pol<waveplate_angle>_<groupnumber>.
The <waveplate_angle>
is the integer part of the angle, e.g. 22, 67, from internal header
ORAC_WAVEPLATE_ANGLE. Subsequent cycles for polarimetry also have the
"_c<cyclenumber>"
suffix, but the cycle comes from steering header POL_CYCLE_NUMBER. When steering header
WAVEPLATE_FLAT is false (0), copies of the flat are made, one for each angle, using the above
nomenclature. Each has its waveplate angle set to its nominal angle. This allows a single
ORAC_WAVEPLATE_ANGLE rule entry irrespective of whether all waveplate angles were combined
to make a flat or not.
Tasks
CCDPACK: MAKEFLAT; KAPPA: FITSMOD, NDFCOPY.
Copyright © 2014–2015 Las Cumbres Observatory Global Telescope Inc.