CLEAN_RESIDUAL

    An  integer code indicating what the Clean image will contain.  Its usage is
    reserved for tests or specific algorithm using the basic CLEAN as an engine.

    -1    The CLEAN image contains only the Clean components, not convolved
        with the Clean beam.
    0     Normal behaviour:  Convolve Clean components with Clean beam and
        add the residuals.
    1     Convolve Clean components, but do not add the residuals.