CLEAN_FRES

    This is the minimal fraction of the peak flux in the dirty map that the pro-
    gram will consider as significant.  Alternatively, an absolute threshold can
    be specified using CLEAN_ARES.  Once this level has been reached the program
    stops subtracting, and starts the restoration phase.  This parameter is nor-
    malized to 1 (neither in % nor in db).  It should usually be of the order of
    magnitude of the inverse of the expected dynamic range of the intensity.

    If 0, CLEAN_ARES will be used instead. If all of CLEAN_NITER, CLEAN_ARES and
    CLEAN_FRES are 0, an absolute residual equal to the noise level will be used
    for CLEAN_ARES.

    Short form is FRES.