An empirical calibration of nebular abundances based on the sulphur emission lines

We present an empirical calibration of nebular abundances based on the strong emission lines of [S II] and [S III] in the red part of the spectrum through the definition of a sulphur abundance parameter S-23. This calibration presents two important advantages against the commonly used one based on the optical oxygen lines: it remains single-valued up to abundances close to solar and is almost independent of the degree of ionization of the nebula.