UVES MASTER FLAT 860nm REDL/REDU 2x2 binning
The pipeline splits red UVES raw frames into two files according to the
two CCDs: one red lower file (right hand side in the raw image) and
one red upper file (left hand side in the raw image).
The pipeline recipe tends to over-subtract the inter-order background
when creating 2x2 master flats so that negative values are possible here.
RED UPPER CCD
RED LOWER CCD