Up: Description of Associated Tasks
As MAKE_MOSAIC, but supports frequency dependent beams (4-D dirty beams).
This task combines individual dirty images and beams corresponding to
various pointing centers into a "mosaic" which is suited for further de-
convolution using the MAPPING program.
Mosaics are ensemble of overlapping fields, with typically half power
primary beam overlap, and similar (but not identical) UV coverages for
each field. Individual images for every field should be created with a
common phase tracking center. The UV_SHIFT, MAP_RA and MAP_DEC vari-
ables in task UV_MAP must be used for this. The image names must derive
from a generic name as follows (e.g. for a generic name MAP)
MAP-1.LMV, MAP-2.LMV, ... MAP-N.LMV
where N is the number of fields.
LET MAP_SIZE 256 512
LET MAP_CELL 0.5
LET UV_SHIFT YES
LET MAP_RA 20:39:10
LET MAP_DEC 68:01:20
LET WCOL 1
FOR I 1 TO 10
LET NAME CONT-'I'
MAKE_MOSAIC produces a combined image (MAP.LMV), a data cube of primary
beams (MAP.LOBE), a data cube of dirty beams (MAP.BEAM), and a weight
image MAP.WEIGHT, which are required for cleaning.
Two parameters are very important in the mosaic creation: the primary
beam width (FWHM), and the truncation threshold of the primary beam. It
is recommended to use a relatively high value for this threshold, 0.2 to
0.4, to avoid contaminating adjacent field in case of pointing errors.