[daip] how to printout the closure phase in AIPS?

[Z.-Q. Shen]

Dear Eric

> All this CLPLT gets right - but
>it takes the uncertainty to be the weight when it should take 1 / sqrt
>(weight).  Thus the error bars plotted by CLPLT are wrong - I will fix
>this.

That's good. Let us know when it is done.

>       Note that weights in AIPS are sometimes rather unrelated to the
>real uncertainty and are usually at best proportional to the
>uncertainty rather than being exactly the correct value.  This makes
>such plotting difficult.

I agree that the relative weight is more important, but to plot the error
it is better to get the absolute one.

>Incoherent averaging produces only amplitude - all averaging to
>produce phase must be done coherently by averaging the real and
>imaginary parts.  The computation of uncertainties is simple.

Could you please tell me more about the calculation of the uncertainty
in the case of coherent (vector) averaging? This is equivalent to asking
how to calculate the uncertainty in the amplitude of a vector. I want to
know how you count the freedom of each visibility data point, 2 or 1?
It would be helpful if you can show me the equations or point me to some
references. My understanding is that for the vector averaging, each
visibility measures both the phase and the amplitude, or the real and
imaginary part. So, the d.o.f. is 2. and then when we estimate the
uncertainty of the mean of Nc data points, the denominator in the
standard deviation expression should be sqrt[2(Nc-1)], right?

-Zhiqiang