WHAM Northern Sky Survey, V-1.1

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^-6^pc, more than 10 million times fainter than the Orion Nebula.