THE GALACTIC DISTRIBUTION OF CHEMICAL-ELEMENTS AS DERIVED FROM B-STARS IN OPEN CLUSTERS .2. NGC-6611, S-285, AND S-289

The chemical composition of the open cluster NGC 6611 and the Sharples s regions S 285 and S 289 have been analysed, and stellar parameters ( effective temperature, gravity, microturbulence) and chemical abundanc es of 4 unevolved B-stars in NGC 6611, 2 B-stars in S 285, and 1 B-sta r in S 289 are given. Line blanketed LTE model atmospheres and NLTE li ne formation calculations were used for the abundance determination of C, N, O, Mg, Al, and Si; LTE line formation calculations were used fo r the abundance determination of Ne, S, and Fe. In agreement with resu lts obtained from B-type stars in the solar neighbourhood and the youn g open cluster NGC 6231 presented in earlier papers, all elements exce pt neon show an average underabundance of 0.1-0.4 dex with respect to the solar value. Among the cluster stars abundance differences of 0.2- 0.7 dex may be observed. First results for the galactic metallicity gr adient show an insignificant value for most observed elements, except for neon and sulfur, which is in contrast to results of analyses of H II regions by Shaver et al. (1983).