The ATCA Forum

Hello everyone,

I thought this might be helpful for other people...

The output from UVRMS looks something like this:
Measured RMS: 0.782
Expected RMS: 1.19

Which is the measured RMS of a single channel for a single 10s integration in Jy.

To calculate uvrms over the observation, the Measured RMS needs to be divided by the sqrt of
number of visibilities to get the expected noise.

The number of visibilities = # channels * records of polarization

The records of polarization is one of the outputs of uvindex.
The input data-set contains the following polarizations:
There were 1806 records of polarization YX
There were 1806 records of polarization XY
There were 1806 records of polarization YY
There were 1806 records of polarization XX


So for example:
when stokes = i
the number of visibilities = 2048*1806 + 2048*1806

Thus the uvrms over the observation: 0.782/sqrt(2048*1806*2) ~0.3 mJy


Thanks Mark and Jamie for all your help.


Cheers
Catarina