Measurements of lines of OH and OH⁺ in the HerPlaNS observations of NGC 6781. The top panel shows the locations of individual PACS spaxels (boxes) and of the central SPIRE SSW and SLW bolometers (circles) for the rim (grey) and centre (white) pointing. In the figure, north is up and the celestial coordinates of the point (0,0) are (α,δ) = (19:18:28.089,6:32:19.262). The footprints are shown over the PACS 70 μm image. Labels indicate specific spaxels. Panels A) and B) show the spatial variation of the OH 119.3μm doublet and panels C) and D) show the OH⁺ 152.99μm line emission in NGC 6781 (rim pointing on the left; centre pointing on the right). Individual PACS spaxels are indicated by the numbers in parentheses. Dust emission is responsible for the differences in the continuum levels.