Processing math: 100%

_MAKE_FLAT_FROM_GROUP_

Makes flats from the current group of frames

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:

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.