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Fig. A.4


Example of the suppression of image background ripples. Top left: small part of a GMRT 150 MHz image based on an eight hour observation, with a low-magnitude but clearly visible ripple in the background. Bottom left: rescaled Fourier transform of the image background, which reproduces the imprinted UV-coverage and reveals several bright spots as well as a bright vertical line (due to residual RFI; see inside cyan rectangle). Bottom right: the same Fourier transform, but with the bright pixels filtered out. Top right: same GMRT 150 MHz image as before, but with all visibilities flagged that correspond to the bright, filtered pixels in the Fourier transform.

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