[daip] about the task EVAUV {External}

[Makoto Miyoshi]

Dear Sirs,

I am emailing because I have a question about the closure residual calculation in EVAUV.

The description of the task, EVAUV, states the following:
"The task will now compute and report closure phase and　amplitude statistics from the "visibilties" of the gain data set (produced by division of the input data by the model, not subtracting (1,0))."
http://www.aips.nrao.edu/cgi-bin/ZXHLP2.PL?EVAUV

In other words, it can be understood for me that at first make the difference between the observed visibility and the visibility corresponding to the image is calculated, and then the closures are calculated from the difference visibilities.

Wouldn't that give a different result than the case we calculated the closures from each of the observed visibilities, visibilities that corresponding to the model image, and then find the mean and standard deviation from the difference between them?

It is confirmed that this is different from the statistics of the difference between the closure phases output using CLPLT from the observed data and those corresponding to a model image.

One of them seems to be wrong. If my understanding is wrong, I am sorry.


Yours sincerely

Makoto Miyoshi
NAOJ, Mitaka


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