Bottom panels: Hammer-Aitoff projection maps, in Galactic coordinates, of the logarithm of the 0.5–2 keV flux limit calculated as the flux at 50% sky covering fraction (see text for details). The left and right panels correspond to values uncorrected and corrected for Galactic absorption, respectively. Six particular regions where the flux limits are increased by bright X-ray sources are marked with red circles; from the north (top) to the south (bottom) they are: the Virgo cluster, Sco X-1, the Vela SNR, the Crab pulsar, the LMC, and the SMC. Top panels: histogram of the logarithm of the flux limit in erg s⁻¹ cm⁻². The colour bar on the X-axis illustrates the intensity scale of the corresponding map in the bottom panels.