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imager.setmfcontrol - Function

2.3.1 Set various cycle control parameters for multi-field and wide-field imageing.


Description

Control parameters for mosaicing or wide-field imaging which are not required in single field deconvolution are set here to streamline the user interface. As multifield and widefield imaging is accomplished by deconvolution in cycles, many of these parameters control how the deconvolution cycles are ended.

cyclefactor: this parameter helps in lowering or increasing the threshold at which the deconvolution cycle will stop and degrid and subtract from the visibilities. For very bad PSFs you may want to reconcile with the visibilties often, thus a larger number is required here...(4 to 5). For very well behaved data you may want to deconvolve deep before reconciling: a lower number is used (1.5 to 2.0).
cyclespeedup: this is used if the PSF is not well behaved and you want clean to raise by 2 the threshold if it has not reached the threshold in this number of iteration
cyclemaxpsffraction: similar to cyclefactor, but this is an explicit fraction of the PSF peak. The final threshold is computed using min( cyclemaxpsffraction, cyclefactor * maxPSFsidelobe). Valid values are between 0.0 and 1.0.
stoplargenegatives: This parameter is exclusively for when using multiscale clean. This is used to stop the component search when the largest scale has found this number of negative components. -1 here means that continue component search even if the largest component is negative.
stoppointmode: Again exclusively for when using multiscale clean. The clean will stop if the smallest scale receives this number of consecutive components.
minpb: This is to defined up to what level the voltage pattern is going to applied when using setvp. The default is 0.1 of the primary beam or the voltage pattern defined for the antenna.
scaletype: This parameter cab be NONE or SAULT. If NONE the image is not scaled, if SAULT is used the image is weighted so that the noise is kept uniform across the image. The next two parameters defines how the SAULT weighting is limited. Obviously then the flux scale is not uniform across the image. To get the right flux multiply the image with the fluxscale image.
constpb: this parameter defines up to what amplitude of the Primary beam the noise floor is kept uniform, when using SAULT as scaletype.
fluxscale: use this to give a filename to store the factor image to apply to the image to get the fluxscale right.
flatnoise: (default true) Set to false if you want clean components for mosaic to be searched in the residual image that is effectively multiplied by the beam2. This means when the noise is determined after the antenna, searching in the optimum domain of signal∕(sigma2). For meter wavelengths where noise is determined by the sky, it is no longer optimal.

Arguments





Inputs

cyclefactor

Cycle threshold = max_resid * min(cyclemaxpsffraction, this * max_sidelobe)

allowed:

double

Default:

1.5

cyclespeedup

Cycle threshold doubles in this number of iterations

allowed:

double

Default:

-1

cyclemaxpsffraction

Cycle threshold = max_resid * min(this, cyclefactor * max_sidelobe)

allowed:

double

Default:

0.8

stoplargenegatives

Stop the multiscale cycle for the first n cycles when a negative comp is found on the largest scale

allowed:

int

Default:

2

stoppointmode

Stop multiscale altogether if the smallest scale recieves this many consecutive components

allowed:

int

Default:

-1

minpb

Minimum PB level to use

allowed:

double

Default:

0.1

scaletype

Image plane flux scale type

allowed:

string

Default:

SAULT

NONE

NONE

constpb

In Sault weighting the flux scale is constant above this PB level

allowed:

double

Default:

0.4

fluxscale

Names of flux scale images for mosaicing

allowed:

stringArray

Default:

flatnoise

Set to false if clean component search is to be done in an optimal signal/noise residual image if true will clean in a constant noise image

allowed:

bool

Default:

true

Returns
bool

Example

 
 
im.setmfcontrol(cyclefactor=2.0, cyclespeedup=niter/10, cyclemaxpsffraction=0.8,  
stoplargenegatives=T, stoppointmode=10, fluxscale=’image.fluxscale’);  
 

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