Darktrail

[julienguy]

Code to fit and correct dark trails.

• desi_compute_dark_trail [-h] -i INFILE [-p PSF] [--plot] -a AMPLIFIER
  • Computes a cross-dispersion profile from a continuum and the trace coordinates saved in a PSF
  • Fits a dark trail assuming some symmetry in the profile.
• py/desispec/darktrail.py contains the function correct_dark_trail that is called by the preprocessing
  if the keywords DARKTRAILAMPX DARKTRAILWIDTHX with X in ABCD are found in the calibration yaml file like https://desi.lbl.gov/trac/browser/calib/desi_spectro_calib/trunk/spec/sp5/r5.yaml

This is a poor man software fix to the readout issue described in #796 .

[sbailey]

Looks good, thanks. Merging now.