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imager.filter - Function

2.3.1 Apply additional weighting by filtering (u-v taper)


Description

Apply visibility tapering to emphasize certain scale structures. The imaging tapers are applied to a Table column called IMAGING_WEIGHT, which may be plotted using tb and pl. plotweights. In addition, this column may be accessed directly using either the table or ms modules. Note that the taper is multiplicative and so the weights must be calculated first using weight. The points are not flagged!

Note that the scale size to be emphasized is given in the image plane as the parameters of the corresponding Gaussian. Note also use of this function provides an optimum detection for the given scale size, which is not the same as requiring that the resulting dirty beam have the specified Gaussian fit. The resultant fitted beam size will very roughly be the quadratic sum of the original beam and the specified beam. If you wish to obtain a specified beam, then the best approach is to perform this calculation and check the value obtained using imager.fitpsf.

Arguments





Inputs

type

Type of filtering or u-v tapering

allowed:

string

Default:

gaussian

bmaj

Major axis of filter

allowed:

any

Default:

variant 1arcsec

bmin

Minor axis of filter

allowed:

any

Default:

variant 1arcsec

bpa

Position angle of filter

allowed:

any

Default:

variant 0deg

async

Run asynchronously in the background

allowed:

bool

Default:

false

Returns
bool

Example

 
 
im.weight(’uniform’)  
im.filter(type=’gaussian’, bmaj=’2.3arcsec’, bmin=’1.67arcsec’,  
bpa=’-34.5deg’)  
 

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