Comparison of the observed limb (μ ≈ 0.145) to disk-centre (μ = 1.0) normalised intensity ratios with different model predictions, for different lines. The solar carbon abundances were set independently for each line and model using disk-centre intensity equivalent widths. The solar carbon abundances and limb viewing angle were allowed to vary within their respective uncertainties, as described in Sect. 3.4. See also Fig. 7.