[daip] Re: Spectral smoothing

[Eric Greisen]

Since the ringing is in the UV data, it is best to remove it there
rather than in the image plane.  I suspect that Hanning in the image
plane with dirty images might also remove the rinnging.  But, after
Clean which is a non-linear process, I would not expect the ringing to
go away completely.  So far as I can tell, XSMTH does what it is told
(in the debugger I checked the convolution func values and they were
0.25, 0.5, 0.25 as expected.  When I did Hanning and Gaussian smooths
and then differenced with COMB there was a real difference that sort
of looked like the source.

Eric Greisen