Volume 501, Number 3, July III 2009
|Page(s)||L19 - L22|
|Published online||22 June 2009|
Letter to the Editor
Stray light correction and contrast analysis of Hinode broad-band images*
Udaipur Solar Observatory, PO Box 198, Udaipur 313004, India e-mail: firstname.lastname@example.org
2 Max-Planck-Institut für Sonnensystemforschung (MPS), Max-Planck-Str. 2, 37191 Katlenburg-Lindau, Germany e-mail: [zakharov;solanki]@mps.mpg.de
3 School of Space Research, Kyung Hee University, Yongin, Gyeonggi 446-701, Korea
Accepted: 12 June 2009
The contrasts of features in the quiet Sun are studied using filtergrams recorded by the broad-band filter imager mounted on the Hinode/Solar Optical Telescope. In a first step, the scattered light originating in the instrument is modeled using Mercury transit data. Combinations of four two-dimensional Gaussians with different widths and weights were employed to retrieve the point-spread functions (PSF) of the instrument at different wavelengths, which also describe instrumental scattered light. The parameters of the PSFs at different wavelengths are tabulated. The observed images were then deconvolved using the PSFs. The corrected images were used to determine the contrasts of features such as bright points and granulation in different wavelength bands. After correction, rms contrasts of the granulation of between 0.11 (at 668 nm) and 0.22 (at 388 nm) were obtained. Similarly, bright point contrasts ranging from 0.07 (at 668 nm) to 0.78 (at 388 nm) are found, which are a factor of 1.8 to 2.8 higher than those obtained before PSF deconvolution. The mean contrast of the bright points is found to be somewhat higher in the CN-band than in the G-band, which confirms theoretical predictions.
Key words: Sun: granulation / Sun: photosphere / instrumentation: high angular resolution
© ESO, 2009
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