  The results from the Supernova Cosmology Project indicate a relation between
cosmic distance and redshift that corresponds to an accelerating Universe, and,
as a consequence, the presence of an energy component with negative pressure.
This necessitates a re-evaluation of such astrophysical luminosities that have
been derived through conventional redshift analyses of, e.g., gamma-ray bursts
and quasars. We have calculated corrected luminosity distances within two
scenarios; the standard one with a non-zero cosmological constant, and the more
recently proposed ``quintessence'', with a slowly evolving energy-density
component. We find luminosity corrections from +30 to -40 per cent for
redshifts with $z=0 - 10$. This finding implicates that the SCP data do not, by
themselves, require a revision of the current, rather qualitative modeling of
gamma-ray bursts and quasar properties.
