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FIT /JVM_FACTOR

        [CLEAN\]FIT [Plane] | [CHANNEL First Last] [FIELD First Last]
      [/THRESHOLD Value] /JVM_FACTOR [NoCircle]

    This option instructs the FIT command to estimate the so-called JvM fac-
    tor (from Jorsater  van Moorsel 1995), which is the ratio of Clean  beam
    area  to Dirty beam area.  The value is returned into the BEAM_JVM vari-
    able.

    The Dirty beam area is an ill-defined quantity (if no  Zero  spacing  is
    included,  the  Dirty  beam  area  tends toward Zero when a sufficiently
    large area is included). It is defined here by integrating  only  up  to
    the first null of the Dirty beam.

    In  case  of Dirty beams presenting shoulders around the main beam, this
    ratio may be used to adjust the contribution of residuals to  the  CLEAN
    image  so that the flux is better preserved.  For well-behaved beams, it
    should be quite close to 1.

    NoCircle is an argument which, if present, indicates that the Clean  and
    Dirty  beam should not be circularized to derive the factor; this should
    be reserved for debugging.


Gildas manager 2023-06-01