Missing Galactic PNe: [S III] Imaging Survey
  The total number of Galactic planetary nebulae is highly uncertain; the most inclusive current catalog contains only ~ 1,500. We will use the PRISM wide-field imager on the 1.83 m Perkins Telescope to conduct a pilot survey of the Galactic plane in search of [S III] emission from planetary nebulae obscured by dust and missed by surveys of H-alpha. We are employing the method of Jacoby & Van de Steene, who surveyed the bulge for 9532 Angstrom [S III] emission. In addition to seeing through more of the extinction, use of the [S III] emission line will a priori reject the most troublesome catalog contaminants: ultracompact H II regions. 
J. Shiode, D. P. Clemens, K. A. Janes, and A. Pinnick