To test for aliasing in a dirty image, calculate images with different cell sizes. An aliased feature will appear to move, while a real one stays at the same angular distance from the image center. The root causes of aliasing are undersampling and the truncation of the sampling at the (u, v) boundaries. Tapering can be used to reduce the latter. Aliasing can occur either during image CLEANing or while the data is being gridded prior to cleaning.
References
Perley, R.; Schwab, F.; and Bridle, A. (Eds.). Ch. 6 in Synthesis Imaging in Radio Astronomy: Third NRAO Summer School, 1988. San Francisco, CA: Astronomical Society of the Pacific, 1989.
Thompson, A. R.; Moran, J. M.; and Swenson, G. W., Jr. Sec. 3.2 in Interferometry and Synthesis in Radio Astronomy. New York: Wiley, pp. 328-335, 1986.
