Individual images for every field should be created with a common phase
tracking center. The UV_SHIFT, MAP_RA and MAP_DEC variables
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.
For example
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' GO UV_MAP NEXT
Then the mosaic must be created using task MAKE_MOSAIC. This task 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.