Astronomical catalogs, data archives, and imaging services (National Astronomical Observatory of Japan)
Collection of compelling HST images and information about image processing techniques.
Catalog of the most beautiful nebulae, star clusters, and galaxies (SEDS)
Images about and from NASA's explorations of space.
Star parallax data and calculations from 1910-1969, originally, the Publications of the Allegheny Observatory of the University of Pittsburgh in 10 volumes.
"Provides basic data, cross-identifications, bibliography and measurements for astronomical objects outside the solar system. "