Photometry and spectroscopy of faint candidate spectrophotometric
  standard DA white dwarfs
  We present precise photometry and spectroscopy for 23 candidate
spectrophotometric standard white dwarfs. The selected stars are distributed in
the Northern hemisphere and around the celestial equators and are all fainter
than r ~ 16.5 mag. This network of stars, when established as standards,
together with the three Hubble Space Telescope primary CALSPEC white dwarfs,
will provide a set of spectrophotometric standards to directly calibrate data
products to better than 1%. These new faint standard white dwarfs will have
enough signal-to-noise ratio in future deep photometric surveys and facilities
to be measured accurately while still avoiding saturation in such surveys. They
will also fall within the dynamic range of large telescopes and their
instruments for the foreseeable future. This paper discusses the provenance of
the observational data for our candidate standard stars. The comparison with
models, reconciliation with reddening, and the consequent derivation of the
full spectral energy density distributions for each of them is reserved for a
subsequent paper.
