Abundances inferred by fitting the observed spectra at the different μ-pointings individually using the 3D hydrodynamic model solar atmosphere and different descriptions for the inelastic O+H collisions (Sect. 2.4.2); our best description is the LCAO+Impulse model, based on physical arguments. The same abundance should be inferred from each μ-pointing (i.e. a flat line is expected). The error bars were calculated by combining in quadrature the uncertainties arising from the finite slit-width (or spread in μ), a 0.1% uncertainty in thecontinuum placement, and the formal fitting error; the first error dominates for the three intermediate pointings, while the last two errors are important for μ ≈ 0.2 and μ ≈ 1.0. Solid lines of weighted best fit are overdrawn, and the dashed lines illustrate the 1 σ uncertainty in the fitted gradients.