Comparison of radial column density profiles of B 68, derived with the LoS-averaged temperature recovery method described in this paper (black solid line, uncertainty range marked by dotted lines), with the assumption of isothermal dust emission (dash-dotted line), and with a ray-tracing approach that takes LoS temperature gradients into account (gray dashed line, uncertainty range marked by gray-shaded area, Nielbock et al. 2012, corrected for OH5 opacities).