Astronomical Applications for "Radial Polarimetry"

摘要: Many objects on the sky exhibit a centrosymmetric polarization pattern, particularly in cases involving single scattering around central source. Utilizing novel liquid crystal device (the ``theta cell'') that transforms coordinate system of linear an image plane from Cartesian to polar, observation patterns can be improved: instead measuring Stokes Q and U sky, one only needs measure Q' new instrument system. This reduces effective exposure time by factor two simplifies modulator design. According manufacturer's specifications measurements lab, applied visible NIR wavelength range. Astronomical science for a``radial polarimeter'' include exoplanet detection, imaging circumstellar disks, reflection nebulae light echos, characterization planetary atmospheres diagnostics solar K-corona. The first astronomical utilizes theta cell radial polarimetry is S5T (Small Synoptic Second Solar Spectrum Telescope), which accurately measures signals near limb sun. These observations are crucial understanding nature origin weak, turbulent magnetic fields photosphere elsewhere universe. A ``radial observing slightly defocused point source performs one-shot full polarimetry. With pupil plane, beam's properties (e.g. calibration purposes) fully controlled through masking.