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<sup>6</sup>/4pi photons/cm<sup>2</sup>/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 the
<a href="https://faun.rc.fas.harvard.edu/dfink/skymaps/halpha/"> H-Alpha Full-Sky Map website</a>. Provenance: . This is a service of NASA HEASARC.