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imager.makemodelfromsd - Function

2.5.1 Make an initial model image from a Single Dish image


Description

This functions use an image from a single dish and make a model (clean component) image out of it. This allows one to use this as the starting model in a deconvoltion function e.g clean or mem This provides an alternative to feather. The difference between the two is that in feather the interferometer image is deconvolved first and the single dish image is put in at the end. Whereas if one starts with a model from the single dish image it will give a different starting point for the deconvolving algorithm to interpolate the missing short baseline.

The function setsdoptions may be used to set a factor by which to scale the SD image, if necessary.

The sdpsf parameter (optional) should be used if an external PSF image of the single dish is needed to calculate the beam parameters of the primary beam of the dish. This is usually needed if the dish image is from a non standard telescope or the beam is not in the CASA system.

The mask is a mask image that may be needed to be used for clean. This is usually the case when the dish image does not fully cover the field defined by defineimage.

Arguments





Inputs

sdimage

Single Dish image

allowed:

string

Default:

modelimage

Name of output image to be used as model

allowed:

string

Default:

sdpsf

PSF of Single Dish if needed

allowed:

string

Default:

maskimage

mask image

allowed:

string

Default:

Returns
bool

Example

 
 
 
im.open(’orion\_only.ms’)  
im.selectvis(field=range(10), spw=range(2))  
im.defineimage(nx=1000, cellx=’1arcsec’, , phasecenter=4, spwid=[0,1])  
im.setvp(dovp=T)  
im.setoptions(ftmachine=’mosaic’)  
im.setscales(nscales=3)  
im.setsdoptions(scale=0.9);  
im.makemodelfromsd(sdimage=’orion\_gbt.im’, modelimage=’orion\_model’, maskimage=’orion.mask’)  
im.clean(algorithm=’mfmultiscale’, model=’orion\_model’,  
residual=’orion.residual’, image=’orion.restored’, gain=0.2, niter=500, mask=’orion.mask’)  
 
 
In the above example we are making a mosaic with the fields 0 to 9. A  
single dish image {\tt orion\_gbt.im} is used scaled down by a factor 0.9 to  
make the initial model that is passed to multi-scale clean.  

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