NGC 6818 - Hubble Space Telescope - JR Wyckoff -([NII]; Halpha; [OIII])
NGC 6818 - Hubble Space Telescope - Rubin et al.
NGC 6818 - Lick Observatory - Benetti et al. - (E-W, 3D projection - [NII]; [OIII]: Halpha)
NGC 6818 - Lick Observatory - Benetti et al. - (N-S, 3D projection - [NII]; [OIII]: Halpha)
NGC 6818 - Hubble Space Telescope - Hajian et al. - (R;G;B = [NII]; [OIII]; lin V)
NGC 6818 - NTT/ESO 1,5m - Schwarz, Corradi, Melnick - (R;G;B = Ha+[NII]; both; OIII)