This primitive control processing for SKY_FLAT recipes through steering headers listed below.

• This primitive is suitable for imaging infrared cameras.

• Processing only occurs for object, sky, or calibration lamp frames.

• The data are deemed to be polarimetry if the frame internal header ORAC_FILTER contains the string "pol".

• A list of the distinct filters within the group is stored in an array stored by reference in the group user header FILTER_LIST.

CYCLE_NUMBER = INTEGER Number of the cycle, a cycle being a set of frames to complete a pass through the recipe. The first cycle is 0. JITTER_NUMBER = INTEGER The number of frames in the jitter. MAKE_FLAT = LOGICAL Whether or not to make the flat. The flat is made once all the jittered target frames in a cycle are available. MASK_OBJECTS = LOGICAL Whether or not to mask the objects. Masking occurs when all the jittered frames in a cycle are available. POL_CYCLE_NUMBER = INTEGER Number of the polarimetry cycle, a cycle being a set of frames to complete a pass through the recipe for all waveplate angles. The first cycle is 0. USE_VARIANCE = LOGICAL Whether or not variance processing is to occur. This equates to argument USEVAR. WAVEPLATE_FLAT = LOGICAL See the argument of the same name. This header merely propagates the value of the argument.