Abstract
ABSTRACT. We present photoelectric spectroscopy observations in the 3400-7400 A range of six Hllregions in the spiral galaxy M101, taken during five observing seasons from 1978 to 1985. Ionic abundances of He+,0+,0++,N+,Ne*,S+ and Ar++ as well as total abundances of N, 0, and He are derived. Gradients in electron temperature, He/H,N/H and 0/H were found. One of the main purposes of this paper is to rederive the helium abundance in the outermost region of M101, NGC 5471, using the high quality observations that have been taken during several years and taking into account the non-linearity of the detector. WO'L : ABUNDANCES - GALAXIES-SPIRAL
