  Exoplanets have sparked interest in extremely high signal-to-noise ratio
spectroscopic observations of very bright stars, in a regime where flux
calibrators, in particular DA white dwarfs, are not available. We argue that
A-type stars offer a useful alternative and reliable space-based
spectrophotometry is now available for a number of bright ones in the range
3<V<8 mag. By means of comparing observed spectrophotometry and model fluxes,
we identify 18 new very-bright trustworthy A-type flux standards for the
optical range (400-800 nm), and provide scaled model fluxes for them. Our tests
suggest that the absolute fluxes for these stars in the optical are reliable to
within 3%. We limit the spectral range to 400-800 nm, since our models have
difficulties to reproduce the observed fluxes in the near-infrared and,
especially, in the near-UV, where the discrepancies rise up to ~ 10%. Based on
our model fits, we derive angular diameters with an estimated accuracy of about
1%.
