THE PERFORMANCE OF MEFOS, THE ESO MULTIOBJECT FIBER SPECTROGRAPH

We are describing a new multi-fibre positioner, MEFOS, that was in gen eral use at the La Silla Observatory, and implemented at the prime foc us of the ESO 3.6 m telescope. It is an arm positioner using 29 arms i n 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 ne eded 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.