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Proceedings Paper

The Irkutsk Barium filter for narrow-band wide-field high-resolution solar images at the Dutch Open Telescope
Author(s): Robert H. Hammerschlag; Valery I. Skomorovsky; Felix C. M. Bettonvil; Galina I. Kushtal; Vyacheslav L. Olshevsky; Robert J. Rutten; Aswin P. L. Jägers; Guus Sliepen; Frans Snik
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Paper Abstract

A wide-field birefringent filter for the barium II line at 455.4nm is developed in Irkutsk. The Barium line is excellent for Doppler-shift measurements because of low thermal line-broadening and steep flanks of the line profile. The filter width is 0.008nm and the filter is tunable over 0.4nm through the whole line and far enough in the neighboring regions. A fast tuning system with servomotor is developed at the Dutch Open Telescope (DOT). Observations are done in speckle mode with 10 images per second and Keller-VonDerLühe reconstruction using synchronous images of a nearby bluecontinuum channel at 450.5nm. Simultaneous observation of several line positions, typically 3 or 5, are made with this combination of fast tuning and speckle. All polarizers are birefringent prisms which largely reduced the light loss compared to polarizing sheets. The advantage of this filter over Fabry-Perot filters is its wide field due to a large permitted entrance angle and no need of polishing extremely precise surfaces. The BaII observations at the DOT occur simultaneously with those of a fast-tunable birefringent H-alpha filter. This gives the unique possibility of simultaneous speckle-reconstructed observations of velocities in photosphere (BaII) and chromosphere (H-alpha).

Paper Details

Date Published: 20 July 2010
PDF: 11 pages
Proc. SPIE 7735, Ground-based and Airborne Instrumentation for Astronomy III, 773585 (20 July 2010); doi: 10.1117/12.858450
Show Author Affiliations
Robert H. Hammerschlag, Utrecht Univ. (Netherlands)
Valery I. Skomorovsky, Institute of Solar-Terrestrial Physics (Russian Federation)
Felix C. M. Bettonvil, Utrecht Univ. (Netherlands)
Galina I. Kushtal, Institute of Solar-Terrestrial Physics (Russian Federation)
Vyacheslav L. Olshevsky, Main Astronomical Observatory (Ukraine)
Robert J. Rutten, Utrecht Univ. (Netherlands)
Univ. of Oslo (Norway)
Aswin P. L. Jägers, Utrecht Univ. (Netherlands)
Guus Sliepen, Utrecht Univ. (Netherlands)
Frans Snik, Utrecht Univ. (Netherlands)

Published in SPIE Proceedings Vol. 7735:
Ground-based and Airborne Instrumentation for Astronomy III
Ian S. McLean; Suzanne K. Ramsay; Hideki Takami, Editor(s)

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