NGC863. Left panel: [S II] emission line map obtained from the Gaussian fitting of the [S II] line from the nebular gas cube spaxel-by-spaxel. The nebular cube was obtained as the difference between the observed cube and stellar cube as described in Appendix A. Central panel: binned [S II] emission line map, from the binned nebular gas cube, after performing an adaptive binning with target S/N([S II]) = 10 to the observed cube, as described. Both panels are close-up of the same region than Fig. 2. Right panel: distributions of S/N of the [S II] line for NGC863, calculated with the Eq. (1). Red distribution corresponds to the S/N([S II]) measured in the observed cube, namely, the S/N([S II]) of the spaxels. Green distribution corresponds to the S/N([S II]) measured in the binned cube, namely, the S/N([S II]) of the bins. The vertical dark green line marks the mean value of the S/N([[S II]]) of the bins, showing that the adaptive binning technique fulfils the goal of reaching a target S/N([S II]) = 10, on average.