Hi,
I have a snapshot observation made with H214 array configuration at cm wavelengths. After usual flagging and calibration, I tried form an mfs continuum image with only ant 6, all visibilities were rejected by invert. uvfstats indicates that only ~20% of data were flagged and uvplt also looks fine. I tried using slop with invert, as suggested by another post in the forum, but failed to work.
Best,
Stephen
Invert rejecting all visibilities
Moderator: Mark.Wieringa
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Re: Invert rejecting all visibilities
Hi Stephen,
Can you please post your inputs to invert in full please, and the terminal output?
Can you please post your inputs to invert in full please, and the terminal output?
cheers
Jamie Stevens
ATCA Senior System Scientist
Jamie Stevens
ATCA Senior System Scientist
Re: Invert rejecting all visibilities
sure.
invert vis=test.uv map=test.imap cell=10 imsize=1025 stokes=i robust=2 select="ant(6)" options=mfs
invert: Revision 1.22, 2016/01/20 03:03:49 UTC
Reading the visibility data ...
Making MFS images
Visibilities accepted: 0
### Warning: Visibilities rejected: 922050
### Fatal Error: No visibilities to map
invert vis=test.uv map=test.imap cell=10 imsize=1025 stokes=i robust=2 select="ant(6)" options=mfs
invert: Revision 1.22, 2016/01/20 03:03:49 UTC
Reading the visibility data ...
Making MFS images
Visibilities accepted: 0
### Warning: Visibilities rejected: 922050
### Fatal Error: No visibilities to map
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Re: Invert rejecting all visibilities
Thanks Stephen. Based on the output, I would first check that antenna 6 is present in the data, because I can't immediately see any problem with the command.
cheers
Jamie Stevens
ATCA Senior System Scientist
Jamie Stevens
ATCA Senior System Scientist
Re: Invert rejecting all visibilities
I saw the data points when plotting out with uvplt
uvplt vis=test.uv device=/xs select="ant(6)" stokes=i options=nobase
so those are not flagged, but for some reason just rejected by invert. I can send around the data for a closer look if needed.
uvplt vis=test.uv device=/xs select="ant(6)" stokes=i options=nobase
so those are not flagged, but for some reason just rejected by invert. I can send around the data for a closer look if needed.
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Re: Invert rejecting all visibilities
Yes, I think we may need to look at the data. What does the output of that uvplt command look like in PGPLOT?
cheers
Jamie Stevens
ATCA Senior System Scientist
Jamie Stevens
ATCA Senior System Scientist
Re: Invert rejecting all visibilities
Hi Jamie,
I've attached a few plots, made with the following commands respectively
uvplt vis=test.uv stokes=i select="ant(6)" nxy=3,2 device=plt1.png/png
uvplt vis=test.uv stokes=i select="ant(6)" nxy=3,2 axis=freq,amp options=nofqav device=plt2.png/png
uvplt vis=test.uv stokes=i select="ant(6)" nxy=3,2 axis=uc,vc options=nofqav device=plt3.png/png
Best,
Stephen
I've attached a few plots, made with the following commands respectively
uvplt vis=test.uv stokes=i select="ant(6)" nxy=3,2 device=plt1.png/png
uvplt vis=test.uv stokes=i select="ant(6)" nxy=3,2 axis=freq,amp options=nofqav device=plt2.png/png
uvplt vis=test.uv stokes=i select="ant(6)" nxy=3,2 axis=uc,vc options=nofqav device=plt3.png/png
Best,
Stephen
- Attachments
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- plt1.png (9.57 KiB) Viewed 13576 times
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- plt2.png (16.55 KiB) Viewed 13576 times
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- plt3.png (7.65 KiB) Viewed 13576 times
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Re: Invert rejecting all visibilities
Hi Stephen,
Have you tried a smaller cellsize? Try 1 or 2 and see what happens. It may be that the long baselines are falling of the edge of the uv grid.
On another note, from your uv plot it doesn't look like you have enough data for a 2-d image. Unless test.uv is just a small subset of the data.
Cheers,
Mark
Have you tried a smaller cellsize? Try 1 or 2 and see what happens. It may be that the long baselines are falling of the edge of the uv grid.
On another note, from your uv plot it doesn't look like you have enough data for a 2-d image. Unless test.uv is just a small subset of the data.
Cheers,
Mark
Re: Invert rejecting all visibilities
Using a small cellsize as suggested works perfectly! Thanks Mark. The observation was a snapshot with very short integration time of a few min only.