The Wisconsin H-Alpha Mapper has been designed to produce a survey of H-Alpha emission from the interstellar medium (ISM) over the entire northern sky. The instrument combines a 0.6 meter telescope and a dual-etalon 15 cm Fabry-Perot spectrometer. In the primary spectral mode, an exposure captures a 200 km/s spectral region with 8-12 km/s velocity resolution from a one-degree beam on the sky. With a large-aperature design and modern CCD technology, WHAM can detect Galactic emission as faint as 0.05 Rayleighs in a 30 second exposure. For gas at 10,000 K, this observed intensity corresponds to an emission measure of about 0.1 cm^-6 pc, more than 10 million times fainter than the Orion Nebula.

The first major product of the WHAM project is an H-Alpha northern sky survey. This new data allows us to explore the spatial and kinematic structure of the warm, ionized component of the ISM in our Galaxy. WHAM surveys ionized hydrogen through the H-Alpha line in a manner analogous to previous surveys of neutral hydrogen made through the 21-cm radio line. By combining our results with 21-cm maps of neutral hydrogen, we can finally explore the relationship between the diffuse ionized and neutral media. A taste of what we hope to learn from such methods can be found in Reynolds, Tufte, Kung, McCullough, & Heiles, 1995, ApJ, 448, 715.

WHAM is a completely remote observing facility. We have taken special care to allow all aspects of operation to be controlled from any location. Our remote capabilities are based on telescope control software written by Jeff Percival that is also used by the WIYN telescope. Although the instrument is locateded in Arizona, nearly all WHAM observations have been operated remotely from Wisconsin.

WHAM spent a year in Wisconsin (November 1995 - November 1996) at Pine Bluff Observatory for testing and software development. It then moved to Kitt Peak , Arizona on November 19, 1996 and began the H-Alpha survey, which took about two years. With the map of Galactic H-Alpha emission under its belt, WHAM continues to gather data to explore the detailed physics of the ionized ISM. Optical emission lines from He, S⁺, N⁺, O, and O⁺⁺ are routinely observed by WHAM.

The WHAM project is funded primarily through grants from the National Science Foundation with additional support provided by the University of Wisconsin Graduate School, the UW Department of Physics, and the UW Department of Astronomy. Much of the hardware was built and assembled by the University of Wisconsin Space Astronomy Laboratory and the Physical Sciences Laboratory.