Low-resolution RP spectra of the O-rich star T Aqr (top panel) and of the C-rich star RU Vir (bottom panel). Thin lines represent epoch spectra, and the thick, darker lines are median spectra. Vertical dashed lines indicate the value of the pseudo-wavelength at the most prominent peaks of the median spectra. The arrows mark the distance in pseudo-wavelength between the two highest peaks, ⟨Δλ⟩_RP, whose value is indicated. This is the adapted version of the figure published as Gaia image of the week IoW_20181115.