We describe a major Anglo-Australian project to undertake a UKST H alpha survey of the Southern Galactic plane, Magellanic clouds and selected regions. The survey will use a new 12 x 12 inch monolithic Her interference filter of high specification and Tech Pan film which offers significant advantages over other emulsions due to its peak sensitivity at Ha and its extremely fine grain, high resolution, exceptional DQE, excellent imaging and low noise. A survey of unprecedented area coverage, depth and resolution should result, superior to any previous optical survey of ionised gas in the galaxy. It is certain to lead to exciting new discoveries and new avenues of research.
