Ca II IRT-1 fluxes for our three instrument samples. RAVE data points are plotted with light blue dots, except for HD 82106 for which a cyan square is used. The fit to them is presented with a dark red line. STELLA-SES data points, both the common sample with RAVE as well as the MK standards are plotted with filled magenta circles, HD 82106 is plotted with a light blue square. PEPSI data points are plotted as follows: blue diamonds are used for dwarfs, yellow diamonds are used for giants, the Sun is plotted with red solar symbol, and HD 82106 is plotted with a violet square. The orange fit is for the giants only. The blue fit is based on both STELLA-SES and PEPSI dwarfs. RAVE fluxes appear on average higher than STELLA-SES and PEPSI fluxes by 19% for IRT-1, 21% for IRT-2, and 25% for IRT-3.