A zoom-in of the optical spectrum covering Hα and the [N ii] and [S ii] line doublets. The weakness of [N ii] and [S ii] relative to Hα indicate that this object is a PN and not a SNR (see Sect. 4 for details). The top panel shows the two-dimensional spectrum at corresponding wavelengths (white pixels indicate large, positive pixel values). The slit height measures 12″, while the spatial extent of the resolved Hα is about 6″.