Total gas opacity at wavelength closest to λ = 1 μm for the Aringer et al. data (left panel) and our new data (right panel). The opacity is colour-coded and is shown vs temperature (x-axis) and gas density (y-axis). All integers on the contour lines are negative (except 0). The temperature and density ranges are 1000 ≤ T ≤ 10 000 K and −18 ≤ log ρ ≤ −6 g cm⁻³, respectively. The two panels use the same ranges and colour palette. The dotted box delimits densities and temperatures in the wind formation region of the model shown in Fig. 4.