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Before applying the antenna solutions to the program sources, you must
set the flux density scale correctly. So far, via SETJY, you have set
the scale for the primary calibrator only. When ATCALIB worked out
solutions for the secondaries, it assumed a flux density of 1 Jy for
each of them (unless you had entered a value into the SU table or
already done a round of ATCALIB and GETJY). Now the solution
amplitudes for the primary and secondary calibrators stored in the SN
table can be ratioed to work out the secondary calibrator flux
densities. The task GETJY is used for this purpose.
- Select the list of secondary calibrators with the sources and
soucode adverbs. If you have a lot of secondaries, it is quicker
to leave soucode blank and select them only with soucode
(provided you used SETJY to give the secondaries a calcode).
- Select the primary calibrator with calsour and calcode.
- You may need to set the uvrange, antennas,
freqid, bif, and eif combinations in the same way that you
did when running ATCALIB and run GETJY several times.
- You may also find it necessary to set a time range with
timerang. For example, if you have observed at low elevations and at a
high frequency, the calibrator will probably have been attenuated by the
atmosphere and the gains will come out appropriately bigger. Ideally,
you should use secondary calibrator scans at the same elevation and
close in time to the observation of the primary calibrator. In
practice, you can only approximate this requirement.
- You can select a specific SN table with snver, or select
all SN tables by leaving it at zero. If you select a specific SN
table, then gain solutions for the primary and secondary calibrators
must be contained in it. It may be necessary for you to delete specific
SN tables before running GETJY if you want most of the available
tables.
GETJY |
sources='0123-23','1322-45',' ' | Select secondary calibrators by name |
soucode='s' | and/or with source code |
calsour='1934-638',' ' | Select primary calibrator by name |
calcode='p' | and/or select with calibrator code |
qual=-1 | Select all qualifiers |
bif=1 | Select IF range |
eif=2 | of interest |
timerang=0 | Select all times |
antennas=0 | Select all antennas |
freqid=1 | One run per freqid |
snver=0 | Select all SN tables or specify |
- Following computation, GETJY enters the new secondary calibrator flux
densities into the source (SU) table and reports them to the user as
well. In addition, GETJY corrects the solution (SN) table(s) to
account for the newly determined flux densities of the secondaries.
Last update : 27/11/93
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Next: INTERPOLATION OF THE GAIN
Up: Analysis of ATCA Data
Previous: Deleting SN tables
nkilleen@atnf.csiro.au