Read all about at astro-ph/0301558
"A Composite H-alpha Template for Microwave Foreground Prediction,"
D. P. Finkbeiner June 2003, ApJS, 146, 407
The full-sky H-alpha map (6' FWHM resolution) is a composite of the Virginia Tech Spectral line Survey (VTSS) in the north and the Southern H-Alpha Sky Survey Atlas (SHASSA) in the south. Stellar artifacts and bleed trails have been carefully removed from these maps. The Wisconsin H-Alpha Mapper (WHAM) survey provides a stable zero-point over 3/4 of the sky on a one degree scale. This composite map can be used to provide limits on thermal bremsstrahlung (free-free emission) from ionized gas known to contaminate microwave-background data. The map (in Rayleighs; 1R=10^6 photons/cm^2/s/sr), an error map, and a bitmask are provided in 8640x4320 Cartesian projections as well as HEALPIX (Nside 256, 512, and 1024) projections on this web site.