This survey was generated from all available ROSAT HRI observations. Data
were mosaicked into 1.1 degree tiles by SkyView. Exposure maps were
generated for each HRI observation using the hriexpmap FTOOL. For each
tile, all observations that might contribute to that tile were located and
added to count and exposure map tiles. Exposures for each observation were
calculated using a nearest neighbor interpolation of the center of the tile
pixels to the exposure map pixels. Counts were computed by projecting the
RA and Decs of each eligible photon into the appropriate tile pixel.
Only photons with a PHA > 3 were included in the mosaic and within each
observation only counts within the region where the exposure was greater
than half the maximum exposure were included. Provenance: Data from GSFC and MPE. <i>SkyView</i> mosaic generated by SkyView.. This is a service of NASA HEASARC.