In addition to the configuration file detailed above, |SExtractor| requires a
file containing the list of parameters that will be listed in the output
catalog for every detection. This allows the software to compute only
catalog parameters that are needed. The name of this
catalog-parameter file is traditionally suffixed with ``.param``, and must
The measurement (or catalog) parameter file
===========================================
In addition to the configuration file detailed above, |SExtractor| requires a file containing the list of measurements ("catalog parameters") that will be listed in the output catalog for every detection. This allows the software to compute only the measurements that are needed. The name of this catalog parameter file is traditionally suffixed with ``.param``, and must
be specified using the ``PARAMETERS_NAME`` config parameter. The full set
of parameters can be queried with the command
...
...
@@ -85,5 +81,22 @@ _WORLD
_SKY, _J2000, _B1950
Measurements are given in celestial (equatorial) coordinates, converted from pixel coordinates using the local Jacobian of the transformation between both systems. Positions and distances are in units of degrees. This requires celestial |WCS| metadata :cite:`2002AA_395_1077C` to be present in the FITS image header(s). _SKY measurements are given in the native world coordinate system. _J2000 and _B1950 measurements are automatically converted from the native |WCS|, taking into account the change of reference frame. In all cases, positions angles are counted East-of-North.
Measurement parameter list
--------------------------
Below is an exhaustive list of all the measurement parameters known to
|SExtractor|. Please refer to the next sections for a detailed description
PHOT\_AUTOPARAMS; by default, PHOT\_AUTOPARAMS is set to 2.5,3.5.
.. figure:: ps/simlostflux.ps
:alt: Flux lost (expressed as a mean magnitude difference) with
different faint-object photometry techniques as a function of total
magnitude (see text). Only isolated galaxies (no blends) of the
simulations have been considered.
:alt: Flux lost (expressed as a mean magnitude difference) with different faint-object photometry techniques as a function of total magnitude (see text). Only isolated galaxies (no blends) of the simulations have been considered.
:width: 15.00000cm
Flux lost (expressed as a mean magnitude difference) with different
Flux lost (expressed as a mean magnitude difference) with different
faint-object photometry techniques as a function of total magnitude
(see text). Only isolated galaxies (no blends) of the simulations
The following parameters are derived from the spatial distribution
:math:`\cal S` of pixels detected above the analysis threshold (see :ref:`description<isophotal_measurements>`). *Unless otherwise noted,
pixel values* :math:`I_i` *are taken from the (filtered) detection image*.
:math:`\cal S` of pixels detected above the analysis threshold (see :ref:`description<isophotal_measurements>`).
.. important::
Unless otherwise noted, pixel values :math:`I_i` are taken from the (filtered) detection image.
.. note::
Unless otherwise noted, all parameter names given below are only prefixes. They must be followed by _IMAGE if the results shall be expressed in pixel coordinates or _WORLD, _SKY, _J2000 or _B1950 for |WCS|_ coordinates (see :ref:`coord_suffix`).