  Quantitative spectroscopy of luminous BA-type supergiants offers a high
potential for modern astrophysics. The degree to which we can rely on
quantitative studies of this class of stars as a whole depends on the quality
of the analyses for benchmark objects. We constrain the basic atmospheric
parameters and fundamental stellar parameters as well as chemical abundances of
the prototype A-type supergiant Deneb to unprecedented accuracy (Teff = 8525
+/- 75 K, log(g) = 1.10 +/- 0.05 dex, M_spec = 19 +/- 3 M_sun, L = 1.96 +/-
0.32 *10^5 L_sun, R = 203 +/- 17 R_sun, enrichment with CN-processed matter) by
applying a sophisticated hybrid NLTE spectrum synthesis technique which has
recently been developed and tested. The study is based on a high-resolution and
high-S/N spectrum obtained with the Echelle spectrograph FOCES on the Calar
Alto 2.2m telescope. Practically all inconsistencies reported in earlier
studies are resolved. Multiple metal ionization equilibria and numerous
hydrogen lines from the Balmer, Paschen, Brackett and Pfund series are brought
into match simultaneously for the stellar parameter determination. Stellar wind
properties are derived from H_alpha line-profile fitting using line-blanketed
hydrodynamic non-LTE models. A self-consistent view of Deneb is thus obtained,
allowing us to discuss its evolutionary state in detail by comparison with the
most recent generation of evolution models for massive stars. (abridged)
