.. _saltillum:

*********
saltillum
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Name
====

saltillum -- Divide an image by its median

Usage
=====

saltillum images outimages outpref mbox (clobber)  (logfile) (verbose)

Parameters
==========


*images*
    String. List of input images including, if necessary, absolute or
    relative paths to the data. Data can be provided as a comma-separated
    list, or a string with a wildcard (e.g. 'images=S20061210*.fits'), or
    a foreign file containing an ascii list of image filenames. For ascii
    list option, the filename containing the list must be provided
    preceded by a '@' character, e.g. 'images=@listoffiles.lis'.

*outimage*
    String. A list of images. Data can be provided as a comma-separated
    list, or a string with a wildcard (e.g. 'outimages=rS20061210*.fits'), or
    a foreign file containing an ascii list of image filenames. For ascii
    list option, the filename containing the list must be provided
    preceded by a '@' character, e.g. 'outimages=@listoffiles.lis'. This list
    must be of the same size as the images argument list.

*outpref*
    String. If the outpref string is non-zero in length and contains
    characters other than a blank space, it will override any value of the
    outimages argument. Output file names will use the name list provided
    in the images argument, but adding a prefix to the basename of
    each  output file defined by outpref. An absolute or relative directory
    path can be included in the prefix, e.g. 'outpref=/Volumes/data/p'.

*mbox*
    Int.  Size of box to be used for median smoothing.

*clobber*
    Hidden boolean. If set to 'yes' files contained within the outpath
    directory will be overwritten by newly created files of the same
    name.

*logfile*
    String. Name of an ascii file for storing log and error messages
    written by the task. The file may be new, or messages can also be
    appended to a pre-existing file.

*(verbose)*
    Boolean. If verbose=n, log messages will be suppressed.

Description
===========


SALTILLUM median smooths an image and then divides the image by that median
smoothing.  The user can set the box size uesd for the smoothing by setting
the mbox variable to the desired box size.

If the file contains a variance frame, it will also apply the correction
to that frame as well.


Examples
========

1. To flat field correct a SALT image::

    --> saltillum images='@images.lis' outimages='' outpref='f'
    mbox=11 clobber='yes' logfile='salt.log' verbose='yes'

Time and disk requirements
==========================

Individual unbinned full frame RSS image files can be 112MB in size. It is
recommended to use workstations with a minimum of 512MB RAM. On a
linux machine with 2.8 Ghz processor and 2 Gb of RAM, one 2051x2051 image can
be processed in 0.31 sec.

Bugs and limitations
====================


Send feedback and bug reports to salthelp@saao.ac.za

See also
========

 :ref:`saltclean` :ref:`saltslot`