Magnetograph observations with the Swedish solar telescope on La Palma

✍ Scribed by Henrik Lundstedt; Anders Johannesson; Göran Scharmer; Jan Olof Stenflo; Ulf Kusoffsky; Birgitta Larsson

• Publisher: Springer
• Year: 1991
• Tongue: English
• Weight: 968 KB
• Volume: 132
• Category: Article
• ISSN: 0038-0938
• DOI: 10.1007/bf00152285

✦ Synopsis

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.