Photometric filters covering the various compiled data sets (details in Sect. 2) compared with spectra of typical stars: Vega (A0V), a G2V star (Sun-like star), and an M5III star. Bottom panel: Gaia DR2 transmissions of the three Gaia passbands and the selected all-sky survey ones (2MASS and WISE). Top panel: selected spectral templates from Pickles (1998), and we overlaid the Fitzpatrick (1999) dust extinction curve and its variations with R₀ for reference. We include GALEX for reference, but we did not include the survey in this work (see Sect. 2).