Figure 5.1: Sky map comparing the 3XMM-DR6 (blue dots) and 3XMM-DR7 (red dots) XMM-Newton pointings in Hammer-Aitoff projection in Galactic coordinates. The galactic longitude ranges from -180 degrees (left) to +180 (right), while the lower and upper poles are at -90 and +90 degrees in galactic latitude respectively.