Spectral region near the gap between CCD 5 and 6 of RGS2, containing the 1s–3p line of O viii at 16.55 Å from the outflow. From top to bottom we show the fluxed spectra (arbitrarily scaled and shifted along the flux axis) for three values of f. Using the conservative setting f = 1, a major part of the spectrum is lost. With f = 0 no data are lost but of course between 16.3 and 16.55 Å the error bars are slightly larger because of the shorter exposure time in that wavelength region.