The fit residuals for models with the OH dust and the radiation field intensity scaled by factors χ = 2 and 3. The values are relative errors I_Obs − I_Mod in per cents of the observed surface brightness I_Obs. The area is this and the subsequent plots of model results is 10′ × 10′ and the plots are centred at coordinates α₂₀₀₀ = 19^h0^m54.3^s, δ₂₀₀₀ = −36°55′22″.