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===============================================================
.. data:: fors_trace_flat
Synopsis
--------
Determine spectral curvature model
Description
-----------
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 User'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
Constructor
-----------
.. method:: cpl.Recipe("fors_trace_flat")
:noindex:
Create an object for the recipe fors_trace_flat.
::
import cpl
fors_trace_flat = cpl.Recipe("fors_trace_flat")
Parameters
----------
.. py:attribute:: fors_trace_flat.param.dispersion
Expected spectral dispersion (Angstrom/pixel) (float; default: 0.0) [default=0.0].
.. py:attribute:: fors_trace_flat.param.startwavelength
Start wavelength in spectral extraction (float; default: 0.0) [default=0.0].
.. py:attribute:: fors_trace_flat.param.endwavelength
End wavelength in spectral extraction (float; default: 0.0) [default=0.0].
.. py:attribute:: fors_trace_flat.param.cdegree
Degree of spectral curvature polynomial (long; default: 0) [default=0].
.. py:attribute:: fors_trace_flat.param.cmode
Interpolation mode of curvature solution applicable to MOS-like data (0 = no interpolation, 1 = fill gaps, 2 = global model) (long; default: 1) [default=1].
The following code snippet shows the default settings for the available
parameters.
::
import cpl
fors_trace_flat = cpl.Recipe("fors_trace_flat")
fors_trace_flat.param.dispersion = 0.0
fors_trace_flat.param.startwavelength = 0.0
fors_trace_flat.param.endwavelength = 0.0
fors_trace_flat.param.cdegree = 0
fors_trace_flat.param.cmode = 1
You may also set or overwrite some or all parameters by the recipe
parameter `param`, as shown in the following example:
::
import cpl
fors_trace_flat = cpl.Recipe("fors_trace_flat")
[...]
res = fors_trace_flat( ..., param = {"dispersion":0.0, "startwavelength":0.0})
.. seealso:: `cpl.Recipe <http://packages.python.org/python-cpl/recipe.html>`_
for more information about the recipe object.
Bug reports
-----------
Please report any problems to `Carlo Izzo <usd-help@eso.org>`_. Alternatively, you may
send a report to the `ESO User Support Department <usd-help@eso.org>`_.
Copyright
---------
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
.. codeauthor:: Carlo Izzo <usd-help@eso.org>
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