dirty image

In radio interferometry, the term dirty image specifically means the image obtained before/without accommodation for the peculiarities of the beam (such as its side lobes, the diffraction akin to that creating Airy disks) and the sampling (the incomplete coverage of the baselines). Specialized image processing (such as the CLEAN algorithm) is applied to reduce these effects and extract an image that more closely matches the signal from the celestial sphere, the result termed a clean image.