NIKA Compton parameter (y) data. From left to right, we show the NIKA MACS J0717.5+3705 input data, its best-fit radial model map, a jackknife map (half difference between two equal data subsets) and the residual between the data and the radial model, δy. The data were smoothed with a 15 arcsec gaussian kernel (FWHM) for visual purposes. The contours are showing the S/N in units of 3σ. The comparison with mock data can be observed in Figure 3.