IAUC 5733 available at Central Bureau for Astronomical Telegrams. IAUC 5733 available at Central Bureau for Astronomical Telegrams.

We present results of a five month spectroscopic monitoring campaign of the Seyfert-1 galaxy NGC 3516. Using a new calibration method and applying a correction for seeing differences during the various observations we can scale the spectra to each other with a much higher accuracy than hitherto achieved. NGC 3516 shows large amplitude variations on

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An observational study of large-scale star formation processes in spiral galaxies with well-defined arm systems is presented. Combining new data on the current massive star formation (from H-alpha imaging) and on the total gas distribution (both atomic and molecular hydrogen, from H I and CO observations), the star formation efficiencies in- and

We present the results of our observations of stars of type O5 and earlier and show that inclusion of the line blocking between 228 and 912 A solves the problem found by Herrero et al. (1992) in the determination of their stellar parameters. We study the influence of the line blocking and other effects on the mass and helium discrepancies and show