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Basic Information on calfit
Task: calfit
Purpose: Fit polynomial to amp/phase data
Categories: calibration
CALFIT is a MIRIAD task which fits polynomials to the wideband data
in a calibration dataset previously made by CALMAKE.
By default, CALFIT uses 2nd order for phases and 0th order for
amplitudes, without phase closure. The resulting fit is stored in
various items in the calibration dataset, and can be over-written.
(See also DELHD, PUTHD, and COPYHD as MIRIAD system utilities)
When a 0th order fit is used for amplitude, CALFIT also displays the
gain factors (Jy/K) for each baseline, sideband and interval. The
dispersion of the phases from the least squares fit (radians) is also
reported.
Key: gcal
The calibration dataset, as produced by CALMAKE. No default.
Key: source
Names of the sources to which the fit is applied.
Default is to select all sources present in the calibration set.
Key: order
The polynomial orders to be fit to the amplitude and phase. The
maximum order for both amplitude and phase is 10. Default: 0,2.
Key: close
If set to true, a baseline based phase closure will be used in the
gain fits.
For 'true', breakpoints are forced to be equal across baselines,
taken from the first baseline found in the database.
Default: false
Key: taver
Taver consists of two numbers, ``tgap'' and ``ttot'', both in minutes,
which are used for vector averaging. If the time interval between
any two successive data points is greater than ``tgap``, or if the
total time between the first data point in a vector average and any
succeeding data point exceeds ``ttot'', then a new vector average is
started.
Default: 0.0,1000.0 (no vector averaging)
Key: mode
Fit 'phase' or 'amplitude'. If nothing specified, both
will be fit. Default: both.
Key: write
A logical, which specifies whether to (over)write the calculated
polynomial coefficients. The item ``pdata'' is used for this.
This allows a ``dryrun'', only showing gains and phase fits.
Default: true.
Key: units
Units to work in. Options are: K, K/Jy, Jy/K. See comments in CALFLAG.
Default: Jy/K.