_SUBTRACT_DARK_

Subtracts a dark frame

Description:

This primitive subtracts from the current frame the most-recent and matching dark frame given by $Cal- >dark method. It reports a successful dark subtraction and the frames concerned.

Since transient ‘hot’ and ‘cold’ pixels can be present despite the application of a bad-pixel mask, the primitive also thresholds the dark-subtracted frame, setting values beyond the limits to be bad (i.e. undefined), to remove these non-physical values. Such values can lead to problems later in the pipeline. In a sense this processing step augments the bad-pixel mask.

Notes:

Output Data

Tasks

CCDPACK: CALCOR; KAPPA: THRESH.