Scroll to navigation



fors_subtract_sky_lss - Subtract sky from calibrated long slit exposure


esorex fors_subtract_sky_lss [OPTIONS] FILE.sof


This recipe is used to subtract the sky from wavelength calibrated scientific spectra produced by the recipe fors_resample. A simple median signal level is subtracted from each image column.

In the table below the MXU acronym can be read alternatively as MOS and LSS, depending on the instrument mode of the input data. The acronym SCI may be read STD in case of standard stars observations.

Note that only LSS or LSS-like MOS/MXU data are to be processed by this recipe.

Input files:

DO category: Type: Explanation: Required: MAPPED_ALL_SCI_MXU Raw Scientific exposure Y

Output files:

DO category: Data type: Explanation: MAPPED_SCI_MXU FITS image Rectified scientific spectra MAPPED_SKY_SCI_MXU FITS image Rectified sky spectra


Note that it is possible to create a configuration file containing these options, along with suitable default values. Please refer to the details provided by the 'esorex --help' command.


The full documentation for the fors pipeline can be downloaded as a PDF file using the following URL:

An overview over the existing ESO pipelines can be found on the web page

Basic documentation about the EsoRex program can be found at the esorex (1) man page.

It is possible to call the pipelines from python using the python-cpl package. See for further information.

The other recipes of the fors pipeline are fors_align_sky(7), fors_align_sky_lss(7), fors_bias(7), fors_calib(7), fors_config(7), fors_dark(7), fors_detect_objects(7), fors_detect_spectra(7), fors_extract(7), fors_extract_objects(7), fors_extract_slits(7), fors_flatfield(7), fors_img_science(7), fors_img_screen_flat(7), fors_img_sky_flat(7), fors_normalise_flat(7), fors_photometry(7), fors_pmos_calib(7), fors_pmos_extract(7), fors_pmos_science(7), fors_remove_bias(7), fors_resample(7), fors_science(7), fors_spec_mflat(7), fors_subtract_sky(7), fors_sumflux(7), fors_trace_flat(7), fors_wave_calib(7), fors_wave_calib_lss(7), fors_zeropoint(7)


fors_subtract_sky_lss 5.3.32


Carlo Izzo <>


Please report any problems to Alternatively, you may send a report to the ESO User Support Department <>.


This file is currently part of the FORS Instrument Pipeline Copyright (C) 2002-2010 European Southern Observatory

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA

5.3.32 fors_subtract_sky_lss