MASH-II: More Planetary Nebulae from the AAO/UKST Hα Survey

We present a supplement to the Macquarie/AAO/Strasbourg H$\alpha$ planetary nebulae (PNe) catalogue (MASH), which we denote MASH-II. The supplement consists of over 300 true, likely and possible new Galactic PNe found after re-examination of the entire AAO/UKST H$\alpha$ survey of the southern Galactic Plane in digital form. We have spectroscopically confirmed over 240 of these new candidates as bona-fide PNe and we include other high quality candidates awaiting spectroscopic confirmation as possible PNe. These latest discoveries largely comprise two distinct groups: small, star-like or moderately resolved PNe at one end and mostly large, extremely low surface brightness PNe at the other. Neither group were easy to discover from simple visual scrutiny of the original survey exposures as for MASH but were relatively straightforward to uncover from the digital images via application of semi-automated discovery techniques. We suspect the few PNe still hidden in the H$\alpha$ survey will lie outside our search criteria or be difficult to find.