Imaging Channel Averaged UV Data

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Imaging Channel Averaged UV Data

Postby bnorfolk » Fri Jan 29, 2021 11:36 am

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
Attachments
non_averaged.png
non_averaged.png (24.71 KiB) Viewed 2815 times
channel_averaged.png
channel_averaged.png (24.48 KiB) Viewed 2815 times
bnorfolk
 
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Re: Imaging Channel Averaged UV Data

Postby Mark.Wieringa » Fri Jan 29, 2021 12:44 pm

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
Mark.Wieringa
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Re: Imaging Channel Averaged UV Data

Postby bnorfolk » Sat Jan 30, 2021 10:34 am

ok great, thanks Mark
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