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Imaging Channel Averaged UV Data

PostPosted: Fri Jan 29, 2021 11:36 am
by bnorfolk
Hi,
I've imported an ATCA uvfits file to CASA and made images for both a non-channel averaged and channel averaged data set. The channel averaged data appears to have a lower SNR, is this a common issue when averaging a poorly uv sampled observation?
Cheers,
Brodie

Re: Imaging Channel Averaged UV Data

PostPosted: Fri Jan 29, 2021 12:44 pm
by Mark.Wieringa
Hi Brodie,

if you have poor uv coverage, using channelised data will help fill the uv plane using multi frequency synthesis. If you average first, you loose this extra coverage.
The poor SNR might just be due to higher sidelobes in the averaged data.
The actual theoretical noise level should be the same, but it will be harder to reach with poorer uv coverage.

Cheers,

Mark

Re: Imaging Channel Averaged UV Data

PostPosted: Sat Jan 30, 2021 10:34 am
by bnorfolk
ok great, thanks Mark