  The shell correction method is revisited. Contrary to the traditional
Strutinsky method, the shell energy is evaluated by an averaging over the
number of particles and not over the single-particle energies, which is more
consistent with the definition of the macroscopic energy. In addition, the
smooth background is subtracted before averaging the sum of single-particle
energies, which significantly improves the plateau condition and allows to
apply the method also for nuclei close to the proton or neutron drip lines. A
significant difference between the shell correction energy obtained with the
traditional and the new method is found in particular for highly degenerated
single-particle spectra (as i.e. in magic nuclei) while for deformed nuclei
(where the degeneracy is lifted to a large extent) both estimates are close,
except in the region of super or hyper-deformed states.
