Comparison of Monte Carlo cumulative θ² distributions (upper panel) for a source with 80% point-like and 20% extended emission and difference between them (lower panel). The characteristic radius of the extension is equal to 0.1° (red dotted), 0.2° (green dashed) or 0.3° (blue dot-dashed), respectively. The extended part of the emission is simulated as a flat disc (dN/dθ² = const.). The purely point-like source is shown as a black solid line. A random mispointing up to 0.03° has been included in the simulations. (This figure is available in color in electronic form).