PLANE

        PLANE

    This is a simple task that subtracts a plane from an  image.  The  plane
    is  determined by least square fitting through all non-blanked pixels of
    the original map, weighted by a weight image. The latter can be used  to
    account  for a non uniform signal to noise ratio, but is more frequently
    used to ignore some areas (typically the sources) in the fit.

    It supersedes an older obsolete version (still available  as  PLANE_OLD)
    which fitted a plane through 3 points of the input image.