  An updated analysis using about 1.5 million events recorded at $\sqrt{s} =
M_Z$ with the DELPHI detector in 1994 is presented. Eighteen infrared and
collinear safe event shape observables are measured as a function of the polar
angle of the thrust axis. The data are compared to theoretical calculations in
${\cal O} (\alpha_s^2)$ including the event orientation. A combined fit of
$\alpha_s$ and of the renormalization scale $x_{\mu}$ in $\cal O(\alpha_s^2$)
yields an excellent description of the high statistics data.
  The weighted average from 18 observables including quark mass effects and
correlations is $\alpha_s(M_Z^2) = 0.1174 \pm 0.0026$. The final result,
derived from the jet cone energy fraction, the observable with the smallest
theoretical and experimental uncertainty, is $\alpha_s(M_Z^2) = 0.1180 \pm
0.0006 (exp.) \pm 0.0013 (hadr.) \pm 0.0008 (scale) \pm 0.0007 (mass)$.
  Further studies include an $\alpha_s$ determination using theoretical
predictions in the next-to-leading log approximation (NLLA), matched NLLA and
$\cal O(\alpha_s^2$) predictions as well as theoretically motivated optimized
scale setting methods. The influence of higher order contributions was also
investigated by using the method of Pad\'{e} approximants. Average $\alpha_s$
values derived from the different approaches are in good agreement.
