Comparison of input (left) and reconstructed (centre, right) visibilities of a 100 mJy Cygnus A, when observed significantly off-axis in the marginally resolved regime (8 arcsec source size and 12 arcsec beam). The integration time and channel bandwidth were chosen to keep smearing below 10% of the synthesised beam at the edge of the main beam. The model visibilities in the right hand panel were constrained to only positive source components. The mean visibility modelling error is 0.9% (centre) and 10% (right).