Solid: Hα line extinction coefficients per m against height for the FCHHT-B model, at line center and in the blue wing at Δλ =  −0.44 and  − 0.74 Å, and the continuous opacity in the adjacent continuum. The dot-dashed curve is the line-center result for LTE. The opacities are multiplied by a scale height of 10⁵ m to make them comparable to the corresponding optical depth scales (dotted curves). The tick marks on the latter correspond to τ_ν = 3,1,0.3. Across the opacity dip due to the temperature minimum the optical depth is τ_ν = 3.5,0.7,0.04 at the three line wavelengths, respectively.