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fors_align_sky_lss - Upgrade wavelength solution using sky lines


esorex fors_align_sky_lss [OPTIONS] FILE.sof


This recipe is used to align the wavelength solution based on the arc lamp exposure on a set of sky lines observed on a scientific exposure.

The input scientific frames are produced by the recipes fors_remove_bias and fors_flatfield. An input catalog of sky lines can be specified, or an internal one is used.

This recipe should be applied to LSS or long-slit like data (MOS/MXU with all slits at the same offset). For multi-slit MOS/MXU data use recipe fors_align_sky instead. Please refer to the FORS PIpeline User´s Manual for more details.

In the table below the MXU acronym can be alternatively read as MOS and LSS, and SCI as STD.

Input files:

DO category: Type: Explanation: Required: SCIENCE_UNBIAS_MXU or SCIENCE_UNFLAT_MXU or STANDARD_UNBIAS_MXU or STANDARD_UNFLAT_MXU Calib Frame with sky lines Y DISP_COEFF_MXU Calib Dispersion solution Y SLIT_LOCATION_MXU Calib Slit location on CCD Y MASTER_SKYLINECAT Calib Catalog of sky lines .

GRISM_TABLE Calib Grism table .

Output files:

DO category: Data type: Explanation: SKY_SHIFTS_LONG_SCI_MXU FITS table Observed sky lines offsets WAVELENGTH_MAP_SCI_MXU FITS image Wavelength mapped on CCD DISP_COEFF_SCI_MXU FITS image Upgraded dispersion solution


--dispersion <float>
Expected spectral dispersion (Angstrom/pixel) (float; default: 0.0). The full name of this option for the EsoRex configuration file is fors.fors_align_sky_lss.dispersion [default = 0.0].
--startwavelength <float>
Start wavelength in spectral extraction (float; default: 0.0). The full name of this option for the EsoRex configuration file is fors.fors_align_sky_lss.startwavelength [default = 0.0].
--endwavelength <float>
End wavelength in spectral extraction (float; default: 0.0). The full name of this option for the EsoRex configuration file is fors.fors_align_sky_lss.endwavelength [default = 0.0].
--skyalign <int>
Polynomial order for sky lines alignment (int; default: 0). The full name of this option for the EsoRex configuration file is fors.fors_align_sky_lss.skyalign [default = 0].
--wcolumn <str>
Name of sky line catalog table column with wavelengths (str; default: ´WLEN´). The full name of this option for the EsoRex configuration file is fors.fors_align_sky_lss.wcolumn [default = WLEN].

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_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_subtract_sky_lss(7), fors_sumflux(7), fors_trace_flat(7), fors_wave_calib(7), fors_wave_calib_lss(7), fors_zeropoint(7)


fors_align_sky_lss 5.5.3


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

5.5.3 fors_align_sky_lss