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Speckle Observations of Solar Granulation

Published online by Cambridge University Press:  19 July 2016

C.R. de Boer  and
F. Kneer
C.R. de Boer
Affiliation:
Universitäts-Sternwarte, Geismarlandstr. 11, D-3400 Göttingen, Federal Republic of Germany
F. Kneer
Affiliation:
Universitäts-Sternwarte, Geismarlandstr. 11, D-3400 Göttingen, Federal Republic of Germany

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Image reconstruction by means of speckle interferometry was successfully used to restore the intensity distribution of solar features and to investigate the morphology and dynamics of small-scale structures in active regions of the Sun. The observations were obtained with the Vacuum Tower Telescope (D = 70 cm, f = 46 m) at Observatorio del Teide, Tenerife, on May 17 and 20, 1991, from a plage region close to a sunspot near disc centre. Sequences of bursts consisting of 100 exposures were recorded with a broad-band filter centred at 550 nm (FWHM ≈ 10 nm, diffraction limit 0.2 arcsec). The pickup unit was a video CCD – system with an exposure time of 4 ms and a frame rate of three pictures per second. A description of the observing procedure and of the data handling can be found in de Boer et al. (1992). To obtain the complex Fourier phases speckle masking (Lohmann et al. 1983) was used. The speckle transfer function of the atmosphere was calculated indirectly using Korff's equation (1973). The Fried parameter r0 was estimated with the spectral ratio technique (von der Lühe 1984). This parameter was sometimes as large as 14 cm. With this the theoretical speckle transfer function could be determined for calculating the corrected Fourier amplitudes of the reconstruction. A new low pass filter, based on the reliability of each individual value in the Fourier plane, was applied to the amplitudes to suppress noise at high wavenumbers.

Type
Imaging Results: Optical and Infrared
Information
Symposium - International Astronomical Union , Volume 158: Very High Angular Resolution Imaging , 1994 , pp. 398 - 400
Copyright
Copyright © Kluwer 1994 

References

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