Faint spectrophotometric standard stars

Absolute spectral energy distributions for 25 stars have been measured with the Double Spectrograph on the 5 m Hale telescope. They have been selected to be spectrophotometric standards for use with the Huble Space Telescope and with ground-based telescopes carrying out HST related work. More than half of these stars have absolute fluxes measured in the ultraviolet with the International Ultraviolet Explorer (IUE). Spectra are shown and smoothed absolute fluxes at continuumm points are listed. Comparisons of these fluxes with those determined elsewhere show that the ones in this paper are systematically brighter by 0.04 mag. (Author)