  We are describing a new multi-fibre positioner, MEFOS, that was in general
use at the La Silla Observatory, and implemented at the prime focus of the ESO
3.6 m telescope. It is an arm positioner using 29 arms in a one degree field.
Each arm is equipped with an individual viewing system for accurate setting and
carries two spectroscopic fibres, one for the astronomical object and the other
one for the sky recording needed for sky subtraction. The spectral fibres
intercept 2.5 arcsec on the sky and run from the prime focus to the Cassegrain,
where the B&C spectrograph is located. After describing the observational
procedure, we present the first scientific results.
