  In this work, we study the motions in the region around the equilateral
Lagrangian equilibrium points L4 and L5, in the framework of the Circular
Planar Restricted Three-Body Problem (hereafter, CPRTBP). We design a
semi-analytic approach based on some ideas by Garfinkel in [4]: the Hamiltonian
is expanded in Poincar\'e-Delaunay coordinates and a suitable average is
performed. This allows us to construct (quasi) invariant tori that are
moderately far from the Lagrangian points L4-L5 and approximate wide tadpole
orbits. This construction provides the tools for studying optimal transfers in
the neighborhood of the equilateral points, when instantaneous impulses are
considered. We show some applications of the new averaged Hamiltonian for the
Earth-Moon system, applied to the setting-up of some transfers which allow to
enter in the stability region filled by tadpole orbits.
