A model fit to the Herschel surface brightness data with an isotropic radiation field four times the ISRF of Mathis et al. (1983). The first row shows the original observations. The other rows show the errors, (I_Obs − I_Mod)/I_Obs, in units of per cent. The second row corresponds to the MWD dust model (Draine 2003), and the bottom row to the OH dust model (Ossenkopf & Henning 1994). To exclude the regions affected by boundary effects, each frame shows the central 8.3′ × 8.3′ area of the whole model that covered an area of 10′ × 10′. To guide the eye, the dashed lines show the outline of the area covered by the NIR observations.