Background methods tested with an empty sky region at Zd < 35°. Top to bottom panels: Wobble map, blind map, and excluded region map. For the excluded region map, the ignored regions (a stripe and two circles) are shaded. The PSF after convolution with a smoothing kernel is depicted in terms of 39% and 68% containment contours. Left panels: ratio of the residuals (skymap-reconstructed background) to the skymap. The blue and red contours indicate ±5% relative flux boundary. Centre panels: test statistic maps computed for the residual counts in the left panels. Right panels: distribution of the test statistic values (blue histogram) compared to the expected normal distribution (red curve). See Sects. 2.3 and 3.1 for details.