Computation

1. After the first run of CLCAL on a group of SN tables, it will issue a message reminding you that you have already applied the SN table(s) once. This is normal and nothing to worry about.
2. You should now self-calibrate the calibrators as a check. Recall that you have generated one solution per antenna averaged over some time interval (probably a scan average). You are now going to apply that solution to the individual visibilities that made up that scan. First self-calibrate the primary calibrator, and then the secondaries.
   • Select the calibrator by selecting it as both the source and the calibrator to be calibrated with the adverbs source, soucode, calsour, and calcode.
   • Select the appropriate freqid to be calibrated (always one at a time).
   • Leave timerang to calibrate all scans.
   • Select interpol='self'. This causes the nearest solution in time (for the specified source) to be selected (this nearest solution is for the calibrator(s) you are trying to self-calibate as well, of course). Thus, each calibrator scan is calibated with the solution from that scan, rather than with an interpolated solution.
   • intparm is not relevant at this stage.
   • Select the desired SN table(s) with snver or leave it at zero, to select all SN tables. SN tables which contain no solutions for the selected sources are safely ignored, so generally leaving this at zero is safe. If you are testing different calibrations, which were written into different SN tables, then this is how you select them.
   • Put gainver=0 (apply SN table solutions to CL table 1) and set gainuse=0 (write solutions into CL table 2).
   • Leave refant at whatever you used in ATCALIB or zero which induces ATCLCAL to work one out for itself.

   Type GO ATCLCAL and the calibrator (do both primary and secondaries) has been self-calibrated. You can write the solutions of as many sources as you like to the same CL table (usually tables 2).

   inname,inclass,inseq,indisk Fill in for averaged data base

   sources='0121-43',' ' Select sources to calibrate by name

   soucode='S' and/or select by source code

   calsour='0121-43' Select desired calibrators by name

   calcode='S' and/or calibrator code

   freqid=3 One freqid per run

   timerang=0 Select time range

   interpol='self' Select self-calibration

   snver=0 All SN tables or select

   gainver=0 Apply solutions to CL table 1

   gainuse=0 Write to CL table 2

   refant=3 Select ref. antenna same as in CALIB

3. Now you must calibrate the program sources.
   • Select the source(s) to be calibrated with the sources and soucode adverbs, and set calsour and calcode to select the desired calibrator. You may want to calibrate more than one source with each secondary in this step.
   • Put interpol='2pt' to select two-point interpolation of the calibrator solutions.

   Leave all the other adverbs as they were for the self-calibration of the calibrators, and run ATCLCAL again. This writes the interpolated solutions into the selected CL table (usually version 2).

   inname,inclass,inseq,indisk Fill in for averaged data base

   sources='0155-48','0101-25',' ' Select sources to calibrate by name

   soucode=' ' and/or select by source code

   calsour='0121-43' Select desired calibrators by name

   calcode='S' and/or calibrator code

   freqid=3 One freqid per run

   timerang=0 Select time range

   interpol='2pt' Select interpolated calibration

   snver=0 All SN tables or select

   gainver=0 Apply solutions to CL table 1

   gainuse=0 Write to CL table 2

   refant=3 Select ref. antenna same as in CALIB

4. Run ATCLCAL as many times are as needed to get through all the different selection criteria you have. For example, with ATCA data you will need to run it for each of the freqids separately (but always writing CL table 2). If you have more secondaries and program sources, run it for each combination of these.