  The X-ray luminosity of black holes is produced through the accretion of
material from their companion stars. Depending on the mass of the donor star,
accretion of the material falling onto the black hole through the inner
Lagrange point of the system or accretion by the strong stellar wind can occur.
Cygnus X-1 is a high mass X-ray binary system, where the black hole is powered
by accretion of the stellar wind of its supergiant companion star HDE226868. As
the companion is close to filling its Roche lobe, the wind is not symmetric,
but strongly focused towards the black hole. Chandra-HETGS observations allow
for an investigation of this focused stellar wind, which is essential to
understand the physics of the accretion flow. We compare observations at the
distinct orbital phases of 0.0, 0.2, 0.5 and 0.75. These correspond to
different lines of sights towards the source, allowing us to probe the
structure and the dynamics of the wind.
