Residual maps of the half differences between the maps made from the first and second half ring projection (from top left to bottom right: 100, 143, 217, 353, 545, 857 GHz) in 1.7 arcmin pixels (Nside = 2048). Note that the CMB channels at 100–217 GHz are all shown on the same color scale. In addition to the noise pattern, which is well traced by the hit maps of Fig. 33, one also sees small differences relative to the signal, when gradients of the signal are large (mostly in the Galactic plane) and sub-pixel effects become quite apparent.