Stacked eROSITA all-sky survey background spectrum (per individual telescope). The blue points are the total measured background. The red points show the background measured during filter wheel closed observations (see Fig. 12). The indicated spectral lines are of instrumental origin (see text). The black points mark the reconstructed (i.e., corrected for vignetting) on-axis photon background spectrum. The horizontal magenta line is the approximate expected particle background level estimated pre-launch (Tenzer et al. 2010).