Directory includes custom pixel flats to be used for Flat Fielding.

The general naming structure is: 
'pixelflat_{spec_name}{dispname}{dichroic}_{binning}_{date}.fits.gz'

spec_name: spectrograph name (e.g. keck_lris_blue)
dispname: metadata dispname (if part of the spectrograph configuration keys)
dichroic: metadata dichroic (if part of the spectrograph configuration keys)
binning: spectral x spatial binning
date: date of the observations

