.TH MSUBSET 1 "June 2010" "Montage 3.3" "Montage"
.SH NAME
mSubset \- Filter an image metadata table down to those records representing FITS files that overlap a footprint on the sky

.SH SYNOPSIS
mSubset [\-d \fIlevel\fP] [\-f] [\-s \fIstatusfile\fP] images.tbl template.hdr subset.tbl

.SH DESCRIPTION
Generates a table of images that is a subset of the input table, containing only those images that cover the area defined by a given FITS header.

.SH OPTIONS
.TP
\-d \fIlevel\fP
Turns on debugging to the specified level (1\-3).
.TP
\-f
Fast mode \- input file must include corners (\-c flag in mImgtbl) to utilize this mode.
.TP
\-s \fIstatusfile\fP
Output and errors are sent to \fIstatusfile\fP instead of to stdout

.SH ARGUMENTS
.TP
images.tbl
ASCII table (generated by \fBmImgtbl\fP) containing metadata for image collection.
.TP
template.hdr
FITS header template defining the area of interest.
.TP
subset.tbl
Path to output table, which will contain only those FITS images covering the area defined by \fItemplate.hdr\fP.

.SH RESULT
\fB[struct stat="OK", count=\fInin\fP, nmatches=\fInout\fP]\fP
.PP
where \fInin\fP is the number of rows found in \fIimages.tbl\fP, and \fInmatches\fP is the number of rows in \fIsubset.tbl\fP, which includes only those images that overlap the area defined by \fItemplate.hdr\fP.

.SH BUGS
The drizzle algorithm has been implemented but has not been tested
in this release.
.PP
If a header template contains carriage returns (i.e., created/modified
on a Windows machine), the cfitsio library will be unable to read it
properly, resulting in the error: [struct stat="ERROR", status=207,
msg="illegal character in keyword"]
.PP
It is best for the background correction algorithms if the area
described in the header template completely encloses all of the input
images in their entirety. If parts of input images are "chopped off"
by the header template, the background correction will be affected. We
recommend you use an expanded header for the reprojection and
background modeling steps, returning to the originally desired header
size for the final coaddition. The default background matching assumes
that there are no non-linear background variations in the individual
images (and therefore in the overlap differences). If there is any
uncertainty in this regard, it is safer to turn on the "level only"
background matching (the "\-l" flag in mBgModel.

.SH COPYRIGHT
2001-2015 California Institute of Technology, Pasadena, California
.PP
If your research uses Montage, please include the following
acknowledgement: "This research made use of Montage. It is funded by
the National Science Foundation under Grant Number ACI-1440620, and
was previously funded by the National Aeronautics and Space
Administration's Earth Science Technology Office, Computation
Technologies Project, under Cooperative Agreement Number NCC5-626
between NASA and the California Institute of Technology."
.PP
The Montage distribution includes an adaptation of the MOPEX algorithm
developed at the Spitzer Science Center.