The ATCA Forum

Hi Nick, Jamie's method will give the precise answer and uvindex will give you a quick estimate of total time on source (unflagged and flagged). Uvindex also gives you the number of 'records' per polarisation - each record here is a spectrum for a single polarisation. If you know the integration tim...

Hi Brodie,

what is the array configuration?

For East-West arrays, you would expect an elongated beam, 1/sin(dec)~6, so 6 to 1 beam axis ratio.
For Hybrid arrays it should be better.

Cheers,

Mark

Hi Rami, yes, you will need to update those parameters to the ones correct for CABB. The section on offsetting the pointing is also no longer relevant, since CABB doesn't have any artefacts at the field centre. That leaves transfix and the gpcal procedure. You can set nfbin for CABB data. The transf...

Hi Rami,

yes, the calibration and imaging works the same for Stokes I and V.
If you need high accuracy in circular polarisation there are some extra steps to take, they are described in the document https://www.atnf.csiro.au/observers/mem ... lguide.pdf

Cheers,

Mark

Hi Brodie, A phase calibrated ATCA observation at 5 GHz or above should have better than 0.5 arcsec position accuracy (usually <0.2"). This is assuming a reasonable beam shape and a config with km baselines. Your beam sizes seem to be in the 1-2" range, which should give sub arcsecond posi...

Hi Brodie, (1,2) yes, generally 7mm data is pretty clean, but you may be unlucky - or there may have been a dropout in the data. I would do manual flagging in this case. Best to inspect the raw, uncalibrated data. Start with simple amp - vs time plots of all the baselines to see if there is anything...

Hi Brodie, the most likely cause for stripes is a feature in the visibilities that is short in time - this could be RFI in target data or a bad calibration solution on the calibrator. So I would suggest a closer look at both the data and the calibration solutions for the 33 GHZ data, followed by som...

Hi Brodie, If the S/N goes down, you're not getting any advantage, so just use the sup=0 image. It could be you can get (slightly) improved S/N with a smaller fwhm value, you can experiment with a few different value to test this. If you know the source is actually an unresolved point source (e.g. G...

Hi Brodie, No, if your brightest source is 2 sigma, there is nothing to clean - any image of a reasonable size should have 4 sigma noise peaks though. You might want to set the limit low enough (4 sigma) that you get a few components in the model so you can run restor and get a beam fit in the heade...

Hi Brodie, not exactly, since it depends on the details of the observation (uv coverage). But after you've made you first image and cleaned it, you know the beam size for those settings and you can estimate from there. A very rough estimate is resolution ~ lamba/Dmax, i.e., observing wavelength divi...