NAME

ndwfsget -- extract FITS cutout image from the NDWFS survey using world coordinate information

USAGE

ndwfsget output ra dec ndwfsget output regions=file

PARAMETERS

output

The output cutout image list. The cutout images are FITS images. If output is "default", the image names have the following form "imroot_coords_filter.fits", where imroot is "NDWFS", coords is an IAU-like field center designation, and filter is the filter id. If output is not "default" the image names in output are used as is. If there are more output images than output image names in output, default names are assigned to the "excess" images.

ra

The right ascension of the center of the region to be extracted in sexigesimal or decimal hours.

dec

The declination of the center of the region to be extracted in sexigesimal or decimal degrees.

rawidth = "10.0", decwidth = "10.0"

The extraction region right ascension and declination widths in arcminutes or x and y widths in pixels. If the radwidth or decwidth value includes a trailing 'p' character, e.g. '600p', then both widths are interpreted as pixels. If the decwidth value is "INDEF", decwidth defaults to the value of rawidth.

fcsystem = "ICRS"

The coordinate system of the center of the region to be extracted. At present only equatorial coordinate systems are supported. The current options are "J2000", "ICRS", and "B1950".

filters = "Bw,R,I"

The filter extraction list. If filters is "all" or "" then data in all filters is extracted, otherwise only data whose filter ids match the ids in filters are extracted. The filter ids must be separated by commas and there must be no internal blanks in the filter list.

regions = "none"

A text file listing the regions to be extracted. The regions file format is described in detail in the description section. If regions is "none" the parameters ra, dec, rawidth, decwidth, fcsystem, and filters define the region to be extracted.

blank = 0.0

The value assigned to undefined pixels in the cutout image.

verbose = yes

Print status messages about the progress of the task ?

DESCRIPTION

The NDWGSGET task extracts FITS cutout images output from the NDWFS survey using region specifications supplied by the user.

A single cutout region can be specified by the ra, dec, rawidth, decwidth, fcsystem, and filters parameters. Multiple cutout regions may be specified in a regions file regions which as 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 field and must be hours and degrees. The right ascension and declination widths must be in arcminutes. 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 list values are optional and default to the value of rawidth, and the values of the fcsystem and filters parameters respectively.

The cutout images are written to output, one cutout image for each specified. If the extraction region overlaps more than one NDWFS survey image, then the cutout image is extracted from the NDWFS survey image which has the largest overlap with the extraction region. The survey images are assumed to have a common projection system, and the cutout image are aligned only to the nearest pixel. Undefined pixels in the cutout images are assigned the value blank.

By default the cutout image names have the form "imroot_coords_filter.fits" where imroot is "NDWFS", coords is an IAU-like coordinate designation, and filter is the filter id. Users may 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" cutout images.

EXAMPLES

1. Extract all the images in the NDWFS survey that overlap the region defined by ra = 14:28:07.0, dec = +34:55:00, rawidth = 2.0, decwidth = 2.0.

cl> ndwfsget "default" 14:28:07.0 +34:55:00 rawidth=2.0 decwidth=2.0 \

filters="Bw,R,I" 

2. Repeat example 2 but specify a region that is 200 pixel in size.

cl> ndwfsget "default" 14:28:07.0 +34:55:00 rawidth=200p decwidth=200p \

filters="Bw,R,I" 

3. Extract cutouts using a regions file. Note that dec/ywidth defaults to the value of ra/xwidth, the coordinate system defaults to the value of the fcsystem parameter, and the filter list default to the values of the filter parameter.

cl> type regfile
14:28:07.0 +34:55:00 1.0 
14:28:07.0 +34:55:05 1.0
00:00:00.0 +00:00:00 1.0
14:28:07.0 +34:54:55 1.0

cl> ndwfsget "default" filters="Bw,R,I" regions=regfile 

TIME REQUIREMENTS

BUGS

SEE ALSO