Hi,
I am reducing some archival ATCA data at 32GHz, array in
config. EW352, source at DEC -30deg, and I have encountered a problem
which I do not know how to solve: though the data reduction looks goods,
when making an image of my .imodel with the task restor I get
''Using Gaussian beam fwhm of NaN by 0.124 arcsec''
so the beam goes to infinite. Any idea of what could be wrong?
I have tried imaging excluding antenna 6, but I still get the same error.
Thanks!
Mar
Infinite beam
Moderator: Mark.Wieringa
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Re: Infinite beam
Hi Mar,
I have also gotten this error on occasion. It usually occurs when the beam is quite elongated, or undersampled in a particular direction.
Thankfully there is an easy enough solution, although it is a bit more complicated than simply using restor. After either the invert or clean steps, you can use the imfit task to measure the beam, using object=beam. You will probably need to select a small central region before this will work, but then you will get something like the following:
Source 1, Object type: beam
Major axis (arcsec): 1.286 +/- 0.001
Minor axis (arcsec): 1.198 +/- 0.001
Position angle (degrees): 2.45 +/- 0.44
You can now take these parameters and input them to restor. From this example you would set fwhm=1.286,1.198 and pa=2.45. This should then give you a good restored image.
I have also gotten this error on occasion. It usually occurs when the beam is quite elongated, or undersampled in a particular direction.
Thankfully there is an easy enough solution, although it is a bit more complicated than simply using restor. After either the invert or clean steps, you can use the imfit task to measure the beam, using object=beam. You will probably need to select a small central region before this will work, but then you will get something like the following:
Source 1, Object type: beam
Major axis (arcsec): 1.286 +/- 0.001
Minor axis (arcsec): 1.198 +/- 0.001
Position angle (degrees): 2.45 +/- 0.44
You can now take these parameters and input them to restor. From this example you would set fwhm=1.286,1.198 and pa=2.45. This should then give you a good restored image.
cheers
Jamie Stevens
ATCA Senior System Scientist
Jamie Stevens
ATCA Senior System Scientist