VizieR Online Data Catalog: WHAM Northern Sky Survey, V-1.1 (Haffner+, 2003)

The Wisconsin Hα Mapper has been designed to produce a survey of Hα emission from the interstellar medium (ISM) over the entire northern sky. The instrument combines a 0.6 meter telescope and a dual-etalon 15cm Fabry-Perot spectrometer. In the primary spectral mode, an exposure captures a 200km/s spectral region with 8-12km/s velocity resolution from a one-degree beam on the sky. With a large-aperture design and modern CCD technology, WHAM can detect Galactic emission as faint as 0.05 Rayleighs in a 30 second exposure. For gas at 10000K, this observed intensity corresponds to an emission measure of about 0.1cm^-6pc, more than 10 million times fainter than the Orion Nebula.

(1 data file).