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       fors_trace_flat - Determine spectral curvature model


       esorex fors_trace_flat [OPTIONS] FILE.sof


       This  recipe  is  used to trace the edges of MOS/MXU flat field slit spectra and determine
       the spectral curvature solution. The input master flat field image, product of the  recipe
       fors_flat,  is  expected  to  be  oriented  with  horizontal  dispersion direction and red
       wavelengths on the right side.

       The input slits location table should be the product of the recipe fors_detect_spectra.

       The input master flat image is shifted one pixel down and is subtracted from the  original
       image.  The  result  is  a  vertical  gradient  map.  Next, the negative values are forced
       positive, to obtain an absolute gradient map. The map is passed with a  horizontal  median
       filter,  and  after  that  the gradient peaks are traced starting from the slits positions
       listed in the input slits location table. The number of pixels to  the  left  and  to  the
       right  of  the  reference pixel is trivially derived from the specified spectral range and
       spectral dispersion.

       The output spectral curvature table contains the coefficients of the polynomial fitting of
       the  found  traces,  while  the  output  trace  table  contains  the traced spectral edges
       positions in CCD (Y) coordinates for  each  spectrum,  and  their  comparison  with  their
       modeling.  A spatial map is also created, where to each CCD pixel is assigned the value of
       the spatial coordinate along the slit (in pixel). For more details  please  refer  to  the
       FORS Pipeline UserĀ“s Manual.

       Note  that  specifying  an  input  GRISM_TABLE  will  set some of the recipe configuration
       parameters to default values valid for a particular grism.

       Again, see the pipeline manual for more details.

       In the table below the MXU acronym can be alternatively read as MOS.

       Input files:

         DO category:               Type:       Explanation:         Required:
         MASTER_SCREEN_FLAT_MXU     Calib       Master flat frame       Y
         SLIT_LOCATION_DETECT_MXU   Calib       Slits location          Y
         GRISM_TABLE                Calib       Grism table             .

       Output files:

         DO category:               Data type:  Explanation:
         CURV_TRACES_MXU            FITS table  Flat field tracings
         CURV_COEFF_MXU             FITS table  Spectral curvature table
         SPATIAL_MAP_MXU            FITS image  Map of spatial coordinate


       --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_trace_flat.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_trace_flat.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_trace_flat.endwavelength
              [default = 0.0].

       --cdegree <int>
              Degree of spectral curvature polynomial (int; default: 0). The full  name  of  this
              option for the EsoRex configuration file is fors.fors_trace_flat.cdegree [default =

       --cmode <int>
              Interpolation mode of curvature solution  applicable  to  MOS-like  data  (0  =  no
              interpolation, 1 = fill gaps, 2 = global model) (int; default: 1). The full name of
              this  option  for  the  EsoRex  configuration  file  is  fors.fors_trace_flat.cmode
              [default = 1].

       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'


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


       fors_trace_flat 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