1998A&AS..133..361H

Deep monochromatic observations are presented for 22 galactic planetary nebulae (PNe) performed through narrow-band interference filters, in the direct imaging mode with i) the New Zealand (MJUO) f/7.8 Mc-Lellan telescope, ii) the Observatoire de Haute Provence (OHP) f/6 120-cm telescope, and iii) and the Siding Spring Observatory (SSO) ATT 2.3 metre telescope. Some of them are observed for the first time. Conspicuous secondary structures are detected far around the conventional nebular pictures. Such features could be relics of early mass ejections during the post-AGB phase of the progenitors. Alternatively, they are more plausibly projections of external loops/bubbles of the ``bar-bell'' shape upon the waist (for face-on PNe). We suggest that such structures (cf. Sh 1-89, Hua, 1997A&AS..125..355H) are intrinsic to all PNe. Their apparently diverse morphologies would ``simply'' result from projections of a same PN intrinsic structure at different view angles onto the plane of sky and with respect to the major axis as well. In addition we report the detection of a new nebula in the field of NGC 3699 (50'' distant). Absolute fluxes are provided for three emission lines.