MOSAIC

        MOSAIC

    Combines individual fields of a mosaic in a single image  for  cleaning.
    This task makes assumptions about file extensions for the images and the
    dirty beams, and computes the primary beams.

    Noting x the direct product, and * a convolution, the combined image is
        Sum (Bj x Ij)
    where Bj is the primary beam of field j, and Ij its dirty  image.   This
    task also compute a weight image, W = 1/Sum(Bj^2).

    If the dirty beams Dj were Diracs, the sky distribution would just be
        S = W . B
    because Ii = Di * (Bi x S)