Flat-fielding

Some recipes create their own flats from the observations themselves, called a self flat, or sky frames within a sequence that dithers to sky, or use a separate observation of a jitter on sky. (There is no support for internal calibrations or dome flats in the recipes.) Whenever a flat is required, recipes access the flat calibration index to find the most recent flat matching the required attributes such as filter.

The current recipes for Michelle mid-infra-red observations do not create or use flat fields.

Creating a flat can be an iterative procedure, involving cleaning, making a first guess, object masking, proper normalisation, and making an improved flat. There are some primitives to bundle the operations including division by the flat field.
[_FLAT_FIELD_MASKED_GROUP_, _FLAT_FIELD_QUADRANT_JITTER_,
_FLAT_FIELD_NCOLOUR_, _DIVIDE_BY_FLAT_, _DIVIDE_BY_FLAT_FROM_GROUP_]

There are variants for certain families of recipes, which marshall the various required subgroups of frames before dividing by the flat field.
[_DIVIDE_BY_FLAT_CHOP_SKY_, _DIVIDE_BY_FLAT_FROM_EXTENDED_,
_DIVIDE_BY_FLAT_NOD_PAIRS_]