June 29: Instructions for imaging and self-calibration of the 3C129 dataset |
James Miller-Jones
######################################## First of all, plot the data Assume i is the catalog number of this SPLIT file Find the relevant number using ucat UVPLT default uvplt getn i dotv 1 docal -1 gainuse 0 sources '' stokes 'i' go This plots amplitude against distance from the centre of the uv-plane. Note the maximum baseline out to which the plot goes, b_max (in klambda). Use this to calculate the required pixel size (3-5 pixels across the resolution element). Also calculate the required image size to image the full primary beam. FWHP beamsize for a 25m dish ~ 45arcmin/frequency(GHz) cellsi = 3600*180/(5*pi*uvmax*1000) imsi = 45*60/(freq(GHz)*cellsi) If there is any bad data, get rid of it with TVFLG ###################################################################### TVFLG default tvflg getn i dparm(3) 1 outfgver 1 go ###################################################################### Now image the source IMAGR default imagr getn i flagver 1 cellsi 0.22 imsi 2048 uvwtfn 'n' dotv 1 niter 2000 boxfile 'PWD:3c129.box' oboxfile boxfile go Image size must be a power of 2. Now interactively CLEAN the image until you don't trust any of the remaining flux. Then stop CLEANing. ###################################################################### Inspect the final image. j is the catalog number of the resulting ICL001 file getn j ; tvin ; tvlo ; tvps Find the rms noise tvwin ; imstat imh or qh: print the max, min flux in the CLEANed image ###################################################################### Plot up the pixel distribution IMEAN default imean getn j doinver 1 dohis 2 dotv 1 pixavg 0 pixstd 0 tvin tvwin go This places the rms noise in the image header, as ACTNOISE ###################################################################### Now self-calibrate the data, using your image as a model CALIB default calib getn i get2n j cmethod 'dft' cmodel 'comp' refant 22 solint 2 solmo 'p' go This writes an SN table and a CALIB file (catalog number k) ###################################################################### Inspect the solutions SNPLT default snplt getn j inext 'sn' inver 1 dotv 1 nplot 9 opty 'phas' go Ensure the phases vary smoothly with time ###################################################################### Re-image the data IMAGR tget imagr getn k niter 5000 go Produces a file ICL001.2, which has catalog number m ###################################################################### Assess the new rms noise IMEAN tget imean getn m go ###################################################################### Try an amplitude and phase selfcal CALIB getn k get2n m solint 20 solmo 'a&p' cparm(2) 1 go Produces new CALIB file (catalog number n) and new SN table ###################################################################### Now you MUST inspect the data to check it did something sensible SNPLT tget snplt getn k inext 'sn' inver 1 dotv 1 nplot 9 opty 'amp' go Ensure the amplitudes are relatively uniform UVPLT tget uvplt getn n go ###################################################################### Now make the final image IMAGR tget imagr getn n go ######################################################################
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