The polarimetric Littrow Spectrograph POLIS is designed for vector polarimetry at high angular and spectral resolution. It measures the magnetic field simultaneously in the photosphere and the chromosphere of the sun. Both branches of the polarimetry unit are dual beam systems with a single rotating modulator for both wavelengths and polarizing

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In addition to the large-scale outflows, which form their round, elliptical, and bipolar shells, planetary nebulae (PNe) also have, usually on smaller scales, pairs of highly collimated outflows, or jets. These jets, as well as the pairs of knots that appear at their tips (very prominent in the low-ionization emission lines), are the subject of the

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I review our knowledge about effective temperatures and masses of massive OB stars paying special attention to results recently obtained using new atmospheric models including sphericity, mass-loss and line-blanketing. The new temperature scales for O dwarfs and supergiants are lower than previously accepted. No systematic mass discrepancy is found

From inversion of a time series of slit spectra, observed in a quiet region of the solar photosphere, averaged models of a granular cell have been obtained showing the stratification of physical quantities versus optical depth and geometrical height. Furthermore a semi-empiric dynamic model of a mean granular cell has been derived and the results