A weighting of visibilities in the reconstruction of images in synthesis imaging. It usually decreases with distance from the phase center, in which case it decreases the influence of the longest (and presumably noisiest) baselines, and also reduces the effect of aliasing at the uv boundary by suppressing small scale sidelobes and increasing the beam width. A Gaussian tapering is often used. However, the optimum taper for a particular observation can only be determined by trial and error.
A tapering function which de-emphasizes data near is used when a large emission region is undersampled, resulting in large undulations in a CLEANed image.
CLEAN Algorithm, Synthesis Imaging
References
Crane, P. and Napier, P. "Sensitivity." Ch. 7 in Synthesis Imaging in Radio Astronomy: Third Summer School, 1988 (Ed. R. A. Perley, F. R. Schwab, and A. H. Bridle). San Francisco, CA: Astronomical Society of the Pacific, 1989.
