extract FITS cutout images from a survey using world coordinate information
Version : 2000.12
Author(s) : Various
License : Free
Website : http://iraf.noao.edu
Installs from Open Source Astronomy for Linux cd 2
Disk space required for installation is 575.51 Kb
This package requires prior installation of iraf
The CUTOUT task extracts FITS cutout images from a list of survey images input and writes the output images to output. The survey images are described in the database file dbfile which is created or updated when CUTOUT is run with opmode ="scan".
The database file contains a description of every survey image. At present this description includes the name of the image, the filter id, the right ascension and declination of the image center in hours and degrees, the coordinate system of the image, the size of the image in pixels, the image projection type, the coordinates of the projection reference point in degrees and degrees, the coordinates of the reference point in pixels and pixels, the x and y image scale in "/pixel, the x and y axes rotation in degrees, and the image extent in ra and dec in degrees and degrees. The database filter ids are read from the image keyword defined by the kwfilter parameter.
A single cutout region is specified by the ra, dec, rawidth, decwidth, fcsystem, and filters parameters. Multiple cutout regions may be defined in the regions file regions which has the following format.
ra1 dec1 ra/xwidth1 [dec/ywidth1 [fcsystem1 [filters1]]] ra2 dec2 ra/xwidth2 [dec/ywidth2 [fcsystem2 [filters2]]] ... raN decN ra/xwidthN [dec/ywidthN [fcsystemN [filtersN]]]
The right ascension and declination values define the center of the extraction region and must be hours and degrees. The right ascension and declination widths must be in arcminutes. The x and y widths must be in pixels. X and Y pixel width values are distinguished from ra and dec width values by a trailing 'p' character. The decwidth / ywidth, coordinate system, and filter id values are optional, and default to the value of rawidth, and the values of the fcsystem and filters parameters respectively.
If opmode = "list" then the names, offsets from the extraction region center in arcminutes or pixels, and filter ids are printed on the screen.
If opmode = "cutout" the FITS image cutouts output are created, one cutout for each filter in filters. If cutmode = "largest" the cutout is extracted from the survey image which has the largest overlap with the extraction region. If cutmode is "collage" then the cutouts are created from all the images which overlap the extraction regions, with images with larger overlap regions taking precedence over those with smaller overlap regions. The survey images are assumed to have a common projection system and cutouts are aligned to the nearest pixel. Undefined pixels in the cutouts are assigned the value blank. If trim = yes then undefined pixels around the edges of the cutout images are removed.
By default the cutout image names are of the form "imroot_coords_filter.fits" where imroot is the values of the parameter imroot, coords is an IAU-like coordinate designation, and filter is the filter id. Users can also specify their own output image names in output. If there are more output images than output image names then default output image names are constructed for the "extra" images.