New polarization data at 850 microns of OMC2 in Orion A are presented. These measurements trace the direction of magnetic fields in the densest parts of the filamentary molecular clouds and form a part of the comparison of magnetic-field directions at various spatial and density scales. They allow us to put constraints on existing models, and

SW Sextantis stars are a relatively large group of cataclysmic variables whose properties contradict all predictions made by the current CV evolution theories. Very little is known about the properties of their accreting white dwarfs and their donor stars, as the stellar components are usually outshone by an extremely bright accretion flow

We present time-resolved optical spectroscopy and photometry of three new relatively bright (V˜14.0-15.5) long-period cataclysmic variables discovered in the Hamburg Quasar Survey: HS 0139+0559, HS 0229+8016 and HS 0506+7725. The orbital periods, 243.2±0.4 min, 233±1 min and 212.6±0.1 min, are determined from radial velocity studies. The light

The mission of the ATST visible spectro-polarimeter (ViSP) is to provide precision measurements of the full state of polarization (Stokes parameters) simultaneously at diverse wavelengths in the visible spectrum and fully resolve (or nearly so) the profiles of spectrum lines originating in the solar atmosphere. We present the instrument science

The SW Sextantis stars are nova-like cataclysmic variables (CVs) which exhibit intricate behaviour which is still a matter of debate. For years the common belief has been that these systems were the "outlaws" of the CVs, mainly because of the lack of an overall understanding. We are now realizing that a large percentage (˜ 30%) of all nova-likes in

The telescope structure including control system and the complete retractable dome of the new 1.5 m solar telescope GREGOR were assembled during 2004 at Izana on Tenerife, Spain. The GREGOR telescope is build by a consortium of the Kiepenheuer Institut fuer Sonnenphysik, the Astrophysikalische Institut Potsdam, the Institut fuer Astrophysik