

NRAO Home > CASA > CASA Toolkit Reference Manual 

imager.filter  Function
2.3.1 Apply additional weighting by filtering (uv 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 uv 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 

bool
Example
im.weight(’uniform’)
im.filter(type=’gaussian’, bmaj=’2.3arcsec’, bmin=’1.67arcsec’,
bpa=’34.5deg’)
__________________________________________________________________
More information about CASA may be found at the
CASA web page
Copyright © 2016 Associated Universities Inc., Washington, D.C.
This code is available under the terms of the GNU General Public Lincense
Home  Contact Us  Directories  Site Map  Help  Privacy Policy  Search