Imaging Channel Averaged UV Data

Got an image problem? Let us help!

Moderator: Mark.Wieringa

Post Reply
bnorfolk
Posts: 45
Joined: Fri May 17, 2019 3:56 pm

Imaging Channel Averaged UV Data

Post 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
Attachments
non_averaged.png
non_averaged.png (24.71 KiB) Viewed 6410 times
channel_averaged.png
channel_averaged.png (24.48 KiB) Viewed 6410 times
Mark.Wieringa
ATCA Expert
Posts: 297
Joined: Mon Feb 08, 2010 1:37 pm

Re: Imaging Channel Averaged UV Data

Post 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
bnorfolk
Posts: 45
Joined: Fri May 17, 2019 3:56 pm

Re: Imaging Channel Averaged UV Data

Post by bnorfolk »

ok great, thanks Mark
Post Reply