The ATCA Forum

Hi Brodie, you are right that you get the most sensitive image (lowest theoretical noise), using sup=0. It will not have the smoothest beam pattern though, so depending on the other sources in the field and the calibration quality, it may be easier to see your source with robust weighting. Robust=2 ...

Hi Brodie, You say you use: clean map=mapfile beam=beamfile out=cleanfile cutoff=(rms from histo) region=percent(33) niters=12000 I would use: clean map=mapfile beam=beamfile out=cleanfile cutoff=(5*rms from histo) region=percent(33) niters=12000 instead. As I said, it is NOT a good idea to clean la...

Hi Brodie, thanks for the image. Judging from the image, your source is only 2-3 times the noise level - unless you have a-priori knowledge that it is in exactly that spot, you wouldn't be able to claim it as a detection (need about 5 sigma). I think, as I mentioned before, the best you can do here ...

Hi Brodie, In both your fits the value is twice the error, so no significant detection. Source fitting doesn't work well below 5 times the noise. If your source is really that faint, your best bet is probably to just get a peak flux and maybe an integrated flux by using kvis to draw a little box aro...

Hi Brodie, yes, if the numbers start to rise, the clean is diverging and there is no point continuing. There can be many reasons for a diverging clean, but common ones are: * Clean area too large for the size of the beam - use options=double in invert * Beam patch too small for side lobes levels in ...

Hi Brodie, what are you using to look at your images? Most image display programs (e.g., kvis, ds9) will show the pixel and world coordinate values of the cursor, so you can just point at your source and read off the pixel offsets. If you need to translate from pixel to world coordinates you can use...

Hi Brodie, I don't think there is a task that does exactly that. A more laborious way to get what you want is to run uvplt with options=log for axis=uu,vv and then for axis=real,imag and then reading both log files into python, discarding the non data lines at the start. You may want to average in t...

Hi Brodie, The 'line type averaging' error appears in a few cases and happens because of the order of operations when reading/averaging/calibrating data on the fly. The easiest way to avoid it is to use uvaver on the data, creating a fully calibrated dataset, and then use that as the input for uvfit...

Hi Brodie, Firstly, it is not really a problem if your source is not in the centre, as long as your image is large enough to let you clean it properly. If you do want to shift the field, the invert offset parameter can be use to specify the offsets in arcsec. As you suggest you can get these by read...

Hi Brodie, unless you are fitting sources far from the phase centre and bandwidth smearing is an issue, it is quicker to just use the line parameter to do some spectral averaging of the data: uvfit vis=myvis object=p line=chan,200,1,10,10 You are allowed 20 million visibilities, so just average thin...