Variations in the dust parameters presented by Planck Collaboration XI (2014), based on a pixel-by-pixel modified blackbody χ² fit (see Eq. (7) and Sect. 6.4 for details). In the top left and right, and the bottom left figures, the observational results are the density of points maps, on which we overplot yellow contours: the central contour encloses 50% of the observed pixels and the external contour 75%. In the bottom right figure, the observational results are the black dots with error bars. In the four figures, the model results are the coloured dots, with the same colour scheme as in Fig. 7. Models normalised to the ratio of Lenz et al. (2017) are shown by magenta and orange dots for p_V/E(B − V) = 9% and 13%, respectively. Those normalised to the ratio of Bohlin et al. (1978) are shown by green and blue dots for p_V/E(B − V) = 9% and 13%, respectively. For comparison, the dark blue squares show the parameters derived from the model of Hensley & Draine (2023). Top left: luminosity vs. temperature. Top right: opacity at 353 GHz vs. temperature. Bottom left: spectral index vs. temperature. Bottom right: E(B-V) vs. optical depth at 353 GHz, models shown for N_H = 10²⁰ H cm⁻².