Illustration of RGS pileup correction for ObsID 0841930901 (see Sect. A.1. The Black spectrum shows the uncorrected RGS1 first-order spectrum, and the uncorrected RGS1 second order spectrum (light blue), a fainter clone of first-order spectrum can be seen at half the wavelengths. The second order spectrum captures the pileup photons that need to be moved into the first order, which then leads to the read curve, the corrected RGS1 spectrum.