man mBackground (1): Remove a background plane from a FITS image

SYNOPSIS

mBackground [-d level] [-n(o-areas)] [-s statusfile] in.fits out.fits A B C

mBackground [-t] [-d level] [-n(o-areas)] [-s statusfile] in.fits out.fits images.tbl corrfile.tbl

DESCRIPTION

Remove a background plane from a FITS image. The background correction applied to the image is specified as Ax+By+C, where (x,y) is the pixel coordinate using the image center as the origin, and (A,B,C) are the background plane parameters specified as linear coefficients.

OPTIONS

-d level: Turns on debugging to the specified level.
-n: Indicates that no area images are present (assumes equal weighting for each data pixel)
-s statusfile: mBackground output and errors will be written to statusfile instead of stdout.
-t: Run in table mode. Starts a group of mBackground runs in parallel, reading off the same pair of tables to determine which files and background corrections to work with. Recommended for running only on grids or parallel processors.

ARGUMENTS

in.fits: Input FITS file
out.fits: Output FITS file
A B C: Corrections (as given by mFitplane or mFitExec)
images.tbl: When run as part of a GRID processing job, mBackground requires the image metadata table to retrieve the filenames of images.
corrections.tbl: When run as part of a GRID processing job, mBackground requires a table of corrections (from mFitplane and mFitExec) to apply to the corresponding image (from images.tbl).

RESULT

Output FITS image with background subtraction applied.

MESSAGES

OK: [struct stat = "OK"]
ERROR: No status file name given
ERROR: Cannot open status file: statusfile
ERROR: No debug level given
ERROR: Debug level string is invalid: string
ERROR: Debug level value cannot be negative
ERROR: Invalid input file filename
ERROR: Invalid output file filename
ERROR: A coefficient string is not a number
ERROR: B coefficient string is not a number
ERROR: C coefficient string is not a number
ERROR: Invalid image metadata file: images.tbl
ERROR: Image table needs columns cntr and fname
ERROR: Hit end of image table without finding file name
ERROR: Need columns: id,a,b,c in corrections file
ERROR: Hit end of corrections table without finding data
ERROR: FITS library error message
ERROR: general error message

EXAMPLES

The following is sample output from mFitplane for a FITS image, in.fits: [struct stat="OK", a=-0.000144415, b=-0.000133642, c=-31.8984, crpix1=758.5, crpix2=-1032, xmin=-758.5, xmax=-349.5, ymin=1032, ymax=1498, xcenter=-555.007, ycenter=1265.26, rms=0.576727]

We use the plane coefficients calculated by mFitplane to subtract the background from the image:

$ mBackground projdir/in.fits bg_removed/in.fits -0.000144415 -0.000133642 -31.8984: [struct stat="OK"]

BUGS

The drizzle algorithm has been implemented but has not been tested in this release.

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"]

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.

COPYRIGHT

2001-2015 California Institute of Technology, Pasadena, California

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."

The Montage distribution includes an adaptation of the MOPEX algorithm developed at the Spitzer Science Center.