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We report the results of narrow band imaging of the bipolar outflow source NGC 2818 in transitions of [NII], [OIII], [SII], and HI. As a consequence, we are able to assess the overall excitation properties of the shell, and determine that line ratios towards the nebular periphery are anomalous, and characteristic of planar shocks with velocity V s ≥ 110 km s −1 . Pre-shock densities are likely to be modest, and of order 10 2 < n p < 10 3 cm −3 . The [SII] imaging is further used to derive adoi:10.1051/aas:1998328 fatcat:x5h2c6j25fh77bqkea33pe4zhy