Search found 296 matches
- Wed Feb 12, 2020 1:46 pm
- Forum: MIRIAD
- Topic: How do you find the total time on source?
- Replies: 3
- Views: 10010
Re: How do you find the total time on source?
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...
- Tue Nov 26, 2019 2:11 pm
- Forum: Calibration
- Topic: Non detection and beam elongation issue
- Replies: 2
- Views: 7550
Re: Non detection and beam elongation issue
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
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
- Fri Nov 01, 2019 10:17 am
- Forum: MIRIAD
- Topic: stokes V imaging
- Replies: 8
- Views: 12406
Re: stokes V imaging
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...
- Fri Nov 01, 2019 8:52 am
- Forum: MIRIAD
- Topic: stokes V imaging
- Replies: 8
- Views: 12406
Re: stokes V imaging
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
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
- Tue Aug 20, 2019 10:08 am
- Forum: Imaging
- Topic: Centering the target
- Replies: 2
- Views: 7057
Re: Centering the target
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...
- Thu Aug 15, 2019 4:20 pm
- Forum: Calibration
- Topic: 33GHz flux discrepancy
- Replies: 3
- Views: 8200
Re: 33GHz flux discrepancy
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...
- Wed Aug 14, 2019 5:04 pm
- Forum: Calibration
- Topic: 33GHz flux discrepancy
- Replies: 3
- Views: 8200
Re: 33GHz flux discrepancy
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...
- Tue Aug 06, 2019 5:14 pm
- Forum: Imaging
- Topic: IMFIT vs UVFIT
- Replies: 10
- Views: 13592
Re: IMFIT vs UVFIT
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...
- Tue Aug 06, 2019 11:04 am
- Forum: Imaging
- Topic: CLEAN iterations
- Replies: 8
- Views: 9573
Re: CLEAN iterations
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...
- Mon Aug 05, 2019 4:47 pm
- Forum: Imaging
- Topic: IMFIT vs UVFIT
- Replies: 10
- Views: 13592
Re: IMFIT vs UVFIT
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...