Generalized Savitzky-Golay polynomials are orthogonal to polynomials up to degree n on a disc, with smoothing weight applied. Upper left panel shows a few representative polynomial kernels (SSG21 in red, SSG42 in dark green, SSG84 in blue) and Gaussian (in black) as a function of radius (scaled to the same FWHM of 800′), lower left shows their harmonic space representation. Right column shows the pre-whitening kernel for the SMICA temperature map on the top (in light blue), and the corresponding composite kernels (WHITE*SSG21, etc.) on the bottom (in the same colours).