CASA and GILDAS handle the weighting scheme slightly differently and
with different conventions for the Robust parameter values.
CASA uses only Briggs weighting, while IMAGER offers the Briggs weight-
ing scheme (obtained for MAP_ROBUST < 0) and a different, more progres-
sive, weighting (obtained for MAP_ROBUST > 0).
For MAP_ROBUST < 0, the corresponding CASA Briggs value can be obtained
by adding 2.
In addition, CASA apparently uses a default value for the size of the UV
cell in Briggs weighting which is about the dish diameter(*). If
MAP_UVCELL is 0, IMAGER will use the same default value. Otherwise, IM-
AGER will use the specified user input.
(*) The default value quoted before is valid for a single field. Howev-
er, the documentation is unclear in this respect and suggests that the
UV cell size depends on the imaged field size. This would be strange,
though. What happens for mosaics is even less clear.
Gildas manager
2023-06-01