  Although the emission of radiation from dark matter annihilation is expected
to be maximized at the Galactic Center, geometric factors and the presence of
point-like and diffuse backgrounds make the choice of the angular window size
to optimize the chance of a signal detection a non-trivial problem. Contrarily
to what is often assumed, we find that the best strategy is to focus on a
window size around the Galactic Center of ~ 1 deg to >~ 30 deg, where the
optimal size depends on the angular distribution of the signal and the
backgrounds. Although our conclusions are general, we illustrate this point in
the particular case of annihilation into two monochromatic photons in the
phenomenologically most interesting range of energy 45 GeV < E < 80 GeV, which
is of great interest for the GLAST satellite. We find for example that Dark
Matter models with sufficiently strong line annihilation signals, like the
Inert Doublet Model, may be detectable without or with very moderate boost
factors.
