  The general expression of the angular distance between two point sources as
measured by an arbitrary observer is given. The modelling presented here is
rigorous, covariant and valid in any space-time. The sources of light may be
located at a finite distance from the observer. The aberration and the
gravitational deflection of light are treated in a unified way. Assuming the
gravitational field to be weak, an explicit expansion of the angular separation
within the post-post-Minkowskian approximation is carried out. The angular
separation within the post-Newtonian approximation truncated at the order
$1/c^3$ is straightforwardly derived.
