Magnetograph observations with the Swedish solar telescope on La Palma |
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| Authors: | Henrik Lundstedt Anders Johannesson Göran Scharmer Jan Olof Stenflo Ulf Kusoffsky Birgitta Larsson |
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| Institution: | (1) Lund Observatory, S-221 00 Lund, Sweden;(2) Stockholm Observatory, S-133 00 Saltsjöbaden, Sweden;(3) Institute of Astronomy, ETH-Zentrum, CH-8092 Zürich, Switzerland;(4) Observatorio del Roque de los Muchachos, Apartado 66, Santa Cruz de la Palma, Islas Canarias, Spain;(5) Institute of Mathematical and Physical Sciences University of Tromsö, N-9001 Tromsö, Norway |
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| Abstract: | A high-resolution videomagnetograph that records the images of opposite circular polarization simultaneously has been constructed for the Swedish vacuum solar telescope at La Palma. Magnetograms are obtained by off-line integration of bursts consisting of typically 50 frames of 20 ms exposures, with bad frames rejected, and the frame-to-frame image motion of the remaining frames compensated for by cross-correlation techniques. The short exposures combined with frame selection and elimination of image motion optimizes the resolution and thereby also the S/N, allowing good magnetograms to be obtained with an effective exposure time of less than 1 s at an image scale of 0.1 pixel–1. The advantages and limitations of the system are discussed and compared with other techniques of making filter magnetograms are discussed. |
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