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\section{The \index{configuration file} configuration file}
\label{chap:configfile}
Each time it is run, {\sc SExtractor} looks for a \index{configuration file} configuration file. If no
\index{configuration file} configuration file is specified in the command-line, it is assumed to
be called ``{\tt default.sex}'' and to reside in the current
directory. If no \index{configuration file} configuration file is found, {\sc SExtractor} will use its own
internal default configuration.
\subsection{Creating a \index{configuration file} configuration file}
{\sc SExtractor} can generate an ASCII dump of its internal default
configuration, using the ``{\tt -d}'' option. By redirecting the standard
output of {\sc SExtractor} to a file, one creates a \index{configuration file} configuration file that
can easily be modified afterwards:
{\tt \% sex -d > default.sex}
A more extensive dump with less commonly used parameters can be generated by
using the ``{\tt -dd}'' option.
\subsection{Format of the \index{configuration file} configuration file}
The format is ASCII. There must be only one parameter set per line,
following the form:
~~~~ {\em Config-parameter ~~~~ Value(s)}
Extra spaces or linefeeds are ignored. Comments must begin with a ``\#''
and end with a linefeed. Values can be of different
types: strings (can be enclosed between double quotes), floats, integers, keywords or Boolean
({\tt Y/y} or {\tt N/n}). Some parameters accept zero or several values, which must then be
separated by commas.
Integers can be given as decimals, in octal form (preceded by digit {\tt O}), or in hexadecimal
(preceded by {\tt 0x}). The hexadecimal format is particularly convenient for writing multiplexed
bit values such as binary masks. Environment variables, written as {\tt \$HOME} or {\tt \$\{HOME\}}
are expanded, and not only for string parameters. Some parameters are assigned default values in
{\sc SExtractor} and can therefore be omitted from the \index{configuration file} configuration file; they are listed in
\S\ref{chap:config}.
\subsection{Configuration parameter list}
\label{chap:config}
Here is a complete list of all the {\em configuration} parameters known to {\sc SExtractor}.
Many of them should be used with their default values. Please refer to the next sections for a
detailed description of their \index{mean} meaning.
% \begin{tabular}{lllp{2.5in}}
\begin{tabbing}
KKKKKKKKKKKKKK \= AAAAAAAAAAAAA \= VVVVVVVVVVVV \= \`TTTTTTTTTTTT \kill
\parhead{Parameter }{ default }{ type }
\parlist{ Description}\\
%\hline
\parhead{{\tt ANALYSIS\_THRESH} }{ {\tt 1.5} }{ {\em floats}\ $(n \le 2)$ }
\parlist{ Threshold (in surface brightness) at
which {\tt CLASS\_STAR} and {FWHM\_} \gam{why underscore?} operate. 1
argument: relative to Background RMS (before filtering).
2 arguments: surface magnitude $\mu$ ($\rm mag\,arcsec^{-2}$), Zero-point (mag).}\\
\parhead{{\tt ASSOC\_DATA} }{ {\tt 2,3,4} }{ {\em integers}\ $(n\le
32)$}
\parlist{ \# of the columns in the
{\tt ASSOC} file that will be copied to the catalogue output.}\\
\parhead{{\tt ASSOC\_NAME} }{ {\tt sky.list} }{ {\em string} }
\parlist{ Name of the {\tt ASSOC} ASCII file.}\\
\parhead{{\tt ASSOC\_PARAMS} }{ {\tt 2,3,4} }{ {\em integers}\ $(2 \le n
\le 3)$}
\parlist{ \# of the columns in the {\tt ASSOC} file that will be used as coordinates
and weight for cross-matching.}\\
\parhead{{\tt ASSOC\_RADIUS} }{ {\tt 2.0} }{ {\em float} }
\parlist{ Search radius (in pixels) for {\tt ASSOC}.}\\
\parhead{{\tt ASSOC\_TYPE} }{ {\tt MAG\_SUM} }{ {\em keyword} }
\parlist{ Method for cross-matching in {\tt ASSOC}:}\\
\pararg {\tt FIRST} { -- keep values corresponding to the first match found,}
\pararg{ \tt NEAREST} {values corresponding to the nearest match found,}
\pararg{ \tt MEAN} {weighted-average values,}
\pararg{ \tt MAG\_MEAN} {exponentially weighted-average values,}
\pararg{ \tt SUM} {sum values,}
\pararg{ \tt MAG\_SUM} {exponentially sum values,}
\pararg{ \tt MIN} {keep values corresponding to the match with minimum weight,}
\pararg{ \tt MAX} {keep values corresponding to the match with maximum weight.}
\parhead{{\tt ASSOCSELEC\_TYPE} }{ {\tt MATCHED} }{ {\em keyword} }
\parlist{ What sources are printed in the output catalogue in case of {\tt ASSOC}:}\\
\pararg{ \tt ALL} {all detections,}
\pararg{ \tt MATCHED} {only matched detections,}
\pararg{ \tt -MATCHED} {only detections that were not matched.}
\parhead{{\tt BACK\_FILTERSIZE} }{ {\tt 3} }{ {\em integers}\ $(n \le 2)$ }
\parlist{ Size, or Width,Height (in background meshes) of the background-filtering mask.}\\
\parhead{{\tt BACK\_SIZE} }{ {\tt 64} }{ {\em integers}\ $(n \le 2)$ }
\parlist{ Size, or Width,Height (in pixels) of a background mesh.}\\
\parhead{{\tt BACK\_TYPE} }{ {\tt AUTO} }{ {\em keywords}\ $(n \le 2)$}
\parlist{ What background is subtracted from the \index{image} images:}\\
\pararg{ \tt AUTO} {the internal,
automatically interpolated \index{background map} background map,}
\pararg{ \tt MANUAL} {a user-supplied constant value provided in {\tt BACK\_VALUE}.}
\parhead{{\tt BACK\_VALUE} }{ {\tt 0.0,0.0} }{ {\em floats}\ $(n \le 2)$ }
\parlist{ in {\tt BACK\_TYPE MANUAL} \index{mode} mode, the constant value to be subtracted
from the \index{image} images.}\\
\parhead{{\tt BACKPHOTO\_THICK} }{ {\tt 24} }{ {\em integer} }
\parlist{ Thickness (in pixels) of the background {\tt LOCAL} annulus.}\\
\parhead{{\tt BACKPHOTO\_TYPE} }{ {\tt GLOBAL} }{ {\em keyword} }
\parlist{ Background used to compute magnitudes:}\\
\pararg{ \tt GLOBAL} {taken directly from the \index{background map} background map,}
\pararg{ \tt LOCAL} {recomputed in a ``rectangular annulus'' around the object.}
\parhead{{\tt CATALOG\_NAME} }{ {\tt test.cat} }{ {\em string}
}
\parlist{ Name of the output catalogue. If the name ``{\tt STDOUT}'' is given and
{\tt CATALOG\_TYPE} is set to {\tt ASCII}, {\tt ASCII\_HEAD}, {\tt ASCII\_SKYCAT}, or {\tt ASCII\_VOTABLE}, the catalogue will be piped to the standard output ({\em stdout})}\\
\parhead{{\tt CATALOG\_TYPE} }{ --- }{ {\em keyword} }
\parlist{ Format of output catalogue (note
that ASCII\* is space and time consuming):}\\
\pararg{ \tt ASCII} {ASCII table,}
\pararg{ \tt ASCII\_HEAD} {as {\tt ASCII},
preceded by a header containing information about the content,}
\pararg{ \tt ASCII\_SKYCAT} {SkyCat ASCII format (WCS coordinates required),}
\pararg{ \tt ASCII\_VOTABLE} {XML-VOTable format, together with meta-data,}
\pararg{ \tt FITS\_1.0} {FITS format as in {\sc SExtractor} 1,}
\pararg{ \tt FITS\_LDAC} {FITS ``LDAC'' format (the original \index{image} image header is copied).}
\parhead{{\tt CHECKIMAGE\_NAME} }{ {\tt check.fits} }{ {\em strings} $(n \le 16)$ }
\parlist{ File name for each ``check-image''.}\\
\parhead{{\tt CHECKIMAGE\_TYPE} }{ {\tt NONE} }{ {\em keywords} $(n \le 16)$}
\parlist{ Type of information in the ``check-images'':}\\
\pararg{ \tt NONE} {no \index{check-image} check-image,}
\pararg{ \tt IDENTICAL} {identical to input \index{image} image (useful for converting formats),}
\pararg{ \tt BACKGROUND} {full-resolution interpolated \index{background map} background map,}
\pararg{ \tt BACKGROUND\_RMS} {full-resolution interpolated background noise map,}
\pararg{ \tt MINIBACKGROUND} {low-resolution \index{background map} background map,}
\pararg{ \tt MINIBACK\_RMS} {low-resolution background noise map,}
\pararg{ \tt -BACKGROUND} {background-subtracted \index{image} image,}
\pararg{ \tt FILTERED} {background-subtracted filtered \index{image} image (requires {\tt FILTER = Y}),}
\pararg{ \tt OBJECTS} {detected objects,}
\pararg{ \tt -OBJECTS} {background-subtracted \index{image} image with detected objects blanked,}
\pararg{ \tt APERTURES} {{\tt MAG\_APER} and {\tt MAG\_AUTO} integration limits,}
\pararg{ \tt SEGMENTATION} {display patches corresponding to pixels attributed to each object.}
\parhead{{\tt CLEAN} }{ {\tt Y} }{ {\em boolean} }
\parlist{ If true, the
catalogue is ``cleaned'' before being written to disk.}\\
\parhead{{\tt CLEAN\_PARAM} }{ {\tt 1.0} }{ {\em float} }
\parlist{ Efficiency of ``cleaning''.}\\
\parhead{{\tt DEBLEND\_MINCONT} }{ {\tt 0.005} }{ {\em float} }
\parlist{ Minimum contrast parameter for \index{deblending} deblending.}\\
\parhead{{\tt DEBLEND\_NTHRESH} }{ {\tt 32} }{ {\em integer} }
\parlist{ Number of \index{deblending} deblending sub-thresholds.}\\
\parhead{{\tt DETECT\_MINAREA} }{ {\tt 5} }{ {\em integer} }
\parlist{ Minimum number of pixels above \index{threshold} threshold triggering detection.}\\
\parhead{{\tt DETECT\_MAXAREA} }{ --- }{ {\em integer} }
\parlist{ Maximum number of pixels
above \index{threshold} threshold triggering detection \gam{What value for infinity?}.}\\
\parhead{{\tt DETECT\_THRESH} }{ {\tt 1.5} }{ {\em floats}\ $(n \le 2)$ }
\parlist{ Detection \index{threshold} threshold. 1 argument: (ADUs or relative to Background RMS, see
{\tt THRESH\_TYPE}). 2
arguments: $\mu$ ($\rm
mag\,arcsec^{-2}$), Zero-point (mag).}\\
\parhead{{\tt DETECT\_TYPE} }{ {\tt \index{CCD} CCD} }{ {\em keyword} }
\parlist{ Type of device that produced the \index{image} image:}\\
\pararg{ \tt \index{CCD} CCD} {linear detector like CCDs or \index{NICMOS} NICMOS,}
\pararg{ \tt PHOTO} {photographic scan.}
\parhead{{\tt FILTER} }{ --- }{ {\em boolean} }
\parlist{ If true, filtering is applied to the data before extraction.}\\
\parhead{{\tt FILTER\_NAME} }{ --- }{ {\em string} }
\parlist{ Name of the file containing the filter definition.}\\
\parhead{{\tt FILTER\_THRESH} }{ }{ {\em floats}\ $(n \le 2)$ }
\parlist{ Lower and higher \index{threshold} thresholds (in background \index{standard deviation} standard deviations) for a pixel
to be considered in filtering (used for retina-filtering only).}\\
\parhead{{\tt FITS\_UNSIGNED} }{ {\tt N} }{ {\em boolean} }
\parlist{ Force 16-bit FITS input data to be interpreted as unsigned integers.}\\
\parhead{{\tt FLAG\_IMAGE} }{ {\tt flag.fits} }{ {\em strings}\ $(n \le 4)$ }
\parlist{ File name(s) of the ``flag-image(s)''.}\\
\parhead{{\tt FLAG\_TYPE} }{ {\tt OR} }{ {\em keyword} }
\parlist{ Combination method for \index{flags} flags on the same object:}\\
\pararg{ \tt OR} {arithmetical OR,}
\pararg{ \tt AND} {arithmetical AND,}
\pararg{ \tt MIN} {minimum of all flag values,}
\pararg{ \tt MAX} {maximum of all flag values,}
\pararg{ \tt MOST} {most common flag value.}
\parhead{{\tt GAIN} }{ }{ {\em float} }
\parlist{ ``Gain'' (conversion factor in $e^-/\mbox{ADU}$) used for error estimates
of {\tt \index{CCD} CCD} magnitudes .}\\
\parhead{{\tt INTERP\_MAXXLAG} }{ {\tt 16} }{ {\em integers}\ $(n \le 2)$ }
\parlist{ Maximum $x$ gap (in pixels) allowed in interpolating the input \index{image} image(s).}\\
\parhead{{\tt INTERP\_MAXYLAG} }{ {\tt 16} }{ {\em integers}\ $(n \le 2)$ }
\parlist{ Maximum $y$ gap (in pixels) allowed in interpolating the input \index{image} image(s).}\\
\parhead{{\tt INTERP\_TYPE} }{ {\tt ALL} }{ {\em keywords}\ $(n \le 2)$ }
\parlist{
Interpolation method from the \index{variance map} variance map(s) (or \index{weight map} weight map(s)):}\\
\pararg{ \tt NONE} {no \index{interpolation} interpolation,}
\pararg{ \tt VAR\_ONLY} {interpolate only the \index{variance map} variance map (detection \index{threshold} threshold),}
\pararg{ \tt ALL} {interpolate both the \index{variance map} variance map and the \index{image} image itself.}
\parhead{{\tt MAG\_GAMMA} }{ }{ {\em float} }
\parlist{ $\gamma$ of the emulsion (takes effect in {\tt PHOTO} \index{mode} mode only).}\\
\parhead{{\tt MAG\_ZEROPOINT} }{ }{ {\em float} }
\parlist{ Zero-point offset to be applied to magnitudes.}\\
\parhead{{\tt MASK\_TYPE} }{ {\tt CORRECT} }{ {\em keyword} }
\parlist{ Method of ``masking'' of \index{neighbour} \index{neighbours} neighbours for photometry:}\\
\pararg{ \tt NONE} {no \index{masking} masking,}
\pararg{ \tt BLANK} {put detected pixels belonging to \index{neighbour} \index{neighbours} neighbours to zero,}
\pararg{ \tt CORRECT} {replace by values of pixels symetric with respect to the source center.}
\parhead{{\tt MEMORY\_BUFSIZE} }{ {\tt 1024} }{ {\em integer} }
\parlist{ Number of scan-lines in the \index{image} image-buffer. Multiply by 4 the frame width to
get equivalent \index{memory} memory space in bytes.}\\
\parhead{{\tt MEMORY\_OBJSTACK} }{ {\tt 3000} }{ {\em integer} }
\parlist{ Maximum number of objects that the object-stack can contain. Multiply by 300 to get
equivalent \index{memory} memory space in bytes.}\\
\parhead{{\tt MEMORY\_PIXSTACK} }{ {\tt 300000} }{ {\em integer} }
\parlist{ Maximum number of pixels that the pixel-stack can contain. Multiply by 16 to 32 to get
equivalent \index{memory} memory space in bytes.}\\
\parhead{{\tt PARAMETERS\_NAME} }{ {\tt default.param} }{ {\em string} }
\parlist{ The name of the file containing the list of parameters that will be computed and put
in the catalogue for each object.}\\
\parhead{{\tt PHOT\_APERTURES} }{ {\tt 5} }{ {\em floats}\ $(n \le 32)$ }
\parlist{ Aperture diameters in pixels (used by {\tt MAG\_APER}).}\\
\parhead{{\tt PHOT\_AUTOPARAMS} }{ {\tt 2.5,3.5} }{ {\em floats}\ $(n=2)$ }
\parlist{ {\tt MAG\_AUTO} controls: scaling parameter $k$ of the 1st order moment, and minimum $R_{min}$
(in units of {\tt A} and {\tt B}).}\\
\parhead{{\tt PHOT\_AUTOAPERS} }{ {\tt 0.0,0.0} }{ {\em floats}\ $(n=2)$ }
\parlist{ {\tt MAG\_AUTO} minimum (circular) aperture diameters: estimation disk, and
measurement disk.}\\
\parhead{{\tt PHOT\_FLUXFRAC} }{ {\tt 0.5} }{ {\em floats}\ $(n \le 32)$ }
\parlist{ Fraction of {\tt FLUX\_AUTO} defining each element of the {\tt FLUX\_RADIUS} vector.}\\
\parhead{{\tt PIXEL\_SCALE} }{ {\tt 1.0} }{ {\em float} }
\parlist{ Pixel size in arcsec (for surface brightness parameters, \index{FWHM} FWHM and star/galaxy separation only).}\\
\parhead{{\tt SATUR\_LEVEL} }{ {\tt 50000.0} }{ {\em float} }
\parlist{ Pixel value above which it is considered saturated.}\\
\parhead{{\tt SEEING\_FWHM} }{ {\tt 1.2} }{ {\em float} }
\parlist{ \index{FWHM} FWHM of stellar \index{image} images in arcsec (only for star/galaxy separation).}\\
\parhead{{\tt STARNNW\_NAME} }{ {\tt default.nnw} }{ {\em string} }
\parlist{ Name of the file containing the neural-network weights for star/galaxy separation.}\\
\parhead{{\tt THRESH\_TYPE} }{ {\tt RELATIVE} }{ {\em keywords}\ $(n
\le 2)$ }
\parlist{ Meaning of the {\tt DETECT\_THRESH} and
{\tt ANALYSIS\_THRESH} parameters:}\\
\pararg{ \tt RELATIVE} {scaling factor to the \index{background RMS} background RMS,}
\pararg{ \tt ABSOLUTE} {absolute level (in ADUs or in surface brightness).}
\parhead{{\tt VERBOSE\_TYPE} }{ {\tt NORMAL} }{ {\tt keyword} }
\parlist{ How much {\sc SExtractor} comments its operations:}\\
\pararg{ \tt QUIET} {run silently,}
\pararg{ \tt NORMAL} {display warnings and limited info concerning the work in progress,}
\pararg{ \tt EXTRA\_WARNINGS} {like {\tt NORMAL}, plus a few more warnings if necessary,}
\pararg{ \tt FULL} {display a more complete information and the principal parameters of all the objects
extracted.}
\parhead{{\tt WEIGHT\_GAIN} }{ {\tt Y} }{ {\em boolean} }
\parlist{ If true, \index{weight map} \index{weight maps} weight maps are considered as \index{gain map} \index{gain maps} \index{gain} gain maps.}\\
\parhead{{\tt WEIGHT\_IMAGE} }{ {\tt weight.fits} }{ {\em strings}\ $(n
\le 2)$ }
\parlist{ File name of the detection and measurement ``weight-image'', respectively.}\\
\parhead{{\tt WEIGHT\_TYPE} }{ {\tt NONE} }{ {\em keywords} $(n \le 2)$ }
\parlist{ Weighting scheme (for single \index{image} image, or detection and
measurement \index{image} images):}\\
\pararg{ \tt NONE} {no weighting,}
\pararg{ \tt BACKGROUND} {variance map derived from the \index{image} image itself,}
\pararg{ \tt MAP\_RMS} {variance map derived from an external RMS map,}
\pararg{ \tt MAP\_VAR} {external \index{variance map} variance map,}
\pararg{ \tt MAP\_WEIGHT} {variance map derived from an external \index{weight map} weight map,}
\parhead{{\tt WRITE\_XML} }{ {\tt N} }{ {\em boolean} }
\parlist{ If true, meta-data will be written in \index{XML} XML-VOTable format.}\\
\parhead{{\tt \index{XML} XML\_NAME} }{ {\tt sex.xml} }{ {\em string} }
\parlist{ File name for the \index{XML} XML output of {\sc SExtractor}.}\\
\end{tabbing}
\gam{I still need to check if parameters are missing with {\tt sex -dd}.}
\footnotetext[1]{Optional parameter}
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