A&A Supplement series, Vol. 129, May I 1998, 637-645
Received May 23; accepted October 06, 1997
J. Pfleiderer - G. KöbInstitut für Astronomie der Leopold-Franzens-Universität Innsbruck, Technikerstraße 25, A-6020 Innsbruck, Austria
We derive deconvolution equations - dirty map and dirty beam -
without use of Fourier transforms. We thus avoid interpolation of
observed complex visibilities (CVs) as well as aliasing effects.
MIM (= minimum information method) implies the modification of
the dirty beam
such that a straightforward deconvolution without constraints gives
a smoothed result. Smoothing can be diminished at edges and point
sources by modification of the dirty map near these features.
We give test examples
in which we discuss in detail the Gibbs phenomenon encountered in any
smoothed deconvolution of sharp features. Finally, we
deconvolve old VLBI observations of
keywords: methods: data analysis -- techniques: image processing, interferometric -- quasars: individual: 3C 309.1