MAP_CONTINUUM GLOBAL

        [ADVANCED\]MAP_CONTINUUM  [DIRTY|CLEAN|Other]  /METHOD GLOBAL [Threshold
    [Nhisto]]

      Compute the integrated spectrum (over the region specified by  CENTER  and
    SIZE  variables), and delineate the line-free region by Gaussian fitting the
    histogram of the spectrum intensity.
      The optional arguments control the algorithm. Threshold is clipping  level
    in sigma units: values in range 2.5 - 5 are usable (default 3.5).  Nhisto is
    the number of histogram bins. The default is to adjust this number depending
    on the number of channels in the data. This is the same algorithm as used in
    UV_CONTINUUM, or in a per pixel mode by the GAUSS method.

      The  continuum  is  then  derived by integrating in the line-free regions.
    This method is fast, and gives a uniform noise since the same  channels  are
    used for all pixels.  It may be inaccurate into several ways:
    -  Regions with strong broad line may still be contaminated by emission from
    the line wings
    - The same applies to regions with line confusion.
    - Continuum emission in regions with no line emission is not derived to  the
    maximum  sensitivity. This can be an issue in case of line confusion at some
    positions.