User Parameters - Continuum imaging

The parameters listed here allow the user to configure the parset and the slurm job for continuum imaging of the science field.

Some of the parameters can be set to blank, to allow cimager to choose appropriate values based on its “advise” capability (which involves examining the dataset and setting appropriate values for some parameters.

When setting the gridding parameters, note that the gridder is currently hardcoded to use WProject. If you want to experiment with other gridders, you need to edit the slurm file or parset yourself (ie. set SUBMIT_JOBS=false to produce the slurm files without submission, then edit and manually submit).

Variable	Default	Parset equivalent	Description
DO_CONT_IMAGING	true	none	Whether to image the science MS
Basic variables
CPUS_PER_CORE_CONT_IMAGING	16	Not for parset	Number of CPUs to use on each core in the continuum imaging.
DATACOLUMN	DATA	datacolumn (cimager)	The column in the measurement set from which to read the visibility data. The default, ‘DATA’, is appropriate for datasets processed within askapsoft, but if you are trying to image data processed, for instance, in CASA, then changing this to CORRECTED_DATA may be what you want.
IMAGE_BASE_CONT	i.cont	Helps form Images.Names (cimager)	The base name for images: if IMAGE_BASE_CONT=i.blah then we’ll get image.i.blah, image.i.blah.restored, psf.i.blah etc
DIRECTION_SCI	none	Images.<imagename>.direction (cimager)	The direction parameter for the images, i.e. the central position. Can be left out, in which case Cimager will get it from the measurement set using the “advise” functionality.
NUM_PIXELS_CONT	4096	Images.shape (cimager)	The number of pixels on the side of the images to be created. If negative, zero, or absent (i.e. NUM_PIXELS_CONT=""), this will be set automatically by the Cimager òÀÜadviseòÀÝ function, based on examination of the MS. Note that this default will be suitable for a single beam, but probably not for an image to be large enough for the full 9 beams. The default value, combined with the default for the cell size, should be sufficient to cover a full field.
CELLSIZE_CONT	10	Images.cellsize (cimager)	Size of the pixels in arcsec. If negative, zero or absent, this will be set automatically by the Cimager òÀÜadviseòÀÝ function, based on examination of the MS. The default is chosen together with the default number of pixels to cover a typical full BETA field.
NUM_TAYLOR_TERMS	2	Images.image.${imageBase}.nterms (cimager) linmos.nterms (linmos (Linear Mosaic Applicator))	Number of Taylor terms to create in MFS imaging. If more than 1, MFS weighting will be used (equivalent to setting Cimager.visweights=MFS in the cimager parset).
MFS_REF_FREQ	no default	visweights.MFS.reffreq (cimager)	Frequency at which continuum image is made [Hz]. This is the reference frequency for the multi-frequency synthesis, which should usually be the middle of the band. If negative, zero, or absent (the default), this will be set automatically to the average of the frequencies being processed.
RESTORING_BEAM_CONT	fit	restore.beam (cimager)	Restoring beam to use: ‘fit’ will fit the PSF to determine the appropriate beam, else give a size (such as 30arcsec, or òÀÜ[30arcsec, 30arcsec, 0deg]òÀÝ).
Gridding parameters
GRIDDER_SNAPSHOT_IMAGING	true	snapshotimaging (Gridders)	Whether to use snapshot imaging when gridding.
GRIDDER_SNAPSHOT_WTOL	2600	snapshotimaging.wtolerance (Gridders)	The wtolerance parameter controlling how frequently to snapshot.
GRIDDER_WMAX	2600	WProject.wmax (Gridders)	The wmax parameter for the gridder.
GRIDDER_NWPLANES	99	WProject.nwplanes (Gridders)	The nwplanes parameter for the gridder.
GRIDDER_OVERSAMPLE	4	WProject.oversample (Gridders)	The oversampling factor for the gridder.
GRIDDER_MAXSUPPORT	512	WProject.maxsupport (Gridders)	The maxsupport parameter for the gridder.
Cleaning parameters
SOLVER	Clean	solver (cimager) (Solvers)	Which solver to use. You will mostly want to leave this as ‘Clean’, but there is a ‘Dirty’ solver available.
CLEAN_ALGORITHM	BasisfunctionMFS	Clean.algorithm (Solvers)	The name of the clean algorithm to use.
CLEAN_MINORCYCLE_NITER	500	Clean.niter (Solvers)	The number of iterations for the minor cycle clean.
CLEAN_GAIN	0.5	Clean.gain (Solvers)	The loop gain (fraction of peak subtracted per minor cycle).
CLEAN_SCALES	“[0,3,10]”	Clean.scales (Solvers)	Set of scales (in pixels) to use with the multi-scale clean.
CLEAN_THRESHOLD_MINORCYCLE	“[30%, 0.9mJy]”	threshold.minorcycle (cimager) (Solvers)	Threshold for the minor cycle loop.
CLEAN_THRESHOLD_MAJORCYCLE	1mJy	threshold.majorcycle (cimager) (Solvers)	The target peak residual. Major cycles stop if this is reached. A negative number ensures all major cycles requested are done.
CLEAN_NUM_MAJORCYCLES	2	ncycles (cimager)	Number of major cycles.
CLEAN_WRITE_AT_MAJOR_CYCLE	false	Images.writeAtMajorCycle (cimager)	If true, the intermediate images will be written (with a .cycle suffix) after the end of each major cycle.
Preconditioning parameters
PRECONDITIONER_LIST	“[Wiener, GaussianTaper]”	preconditioner.Names (Solvers)	List of preconditioners to apply.
PRECONDITIONER_GAUSS_TAPER	“[30arcsec, 30arcsec, 0deg]”	preconditioner.GaussianTaper (Solvers)	Size of the Gaussian taper - either single value (for circular taper) or 3 values giving an elliptical size.
PRECONDITIONER_WIENER_ROBUSTNESS	0.5	preconditioner.Wiener.robustness (Solvers)	Robustness value for the Wiener filter.
PRECONDITIONER_WIENER_TAPER	“”	preconditioner.Wiener.taper (Solvers)	Size of gaussian taper applied in image domain to Wiener filter. Ignored if blank (ie. òÀÜòÀÝ).