Tuesday, May 22, 2007

CPARM(2) and Self Cal

Emily read in the GMRT documentation that, when doing A&P self calibration, you should set CPARM(2) = 1, which means you would 'normalize gains'. However, we didn't really understand what this meant, and didn't understand why we were doing it. Today I asked Miller Goss, who's visiting UW from NRAO, and he said...

You should set CPARM(2) = 1 only if you don't trust your amplitudes initially! If you think your original amplitude calibration is not so good, say in the case of VLBA data or certain frequencies at the GMRT, you might want to set it.

However, at the VLA, you should set CPARM(2) = 0 because your original amplitude calibration was really quite decent. (At least at L and C band, not sure about crazy other frequencies!)

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