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. SkyView mosaic generated by SkyView.. This is a service of NASA HEASARC.