Volume 454, Number 3, August II 2006
|Page(s)||1011 - 1019|
|Section||Instruments, observational techniques, and data processing|
|Published online||17 July 2006|
Speckle reconstruction of photometric data observed with adaptive optics
Institut für Astrophysik, Freidrich-Hund-Platz 1, 37077 Göttingen, Germany e-mail: [kgp;msailer]@astro.physik.uni-goettingen.de
Accepted: 3 April 2006
To achieve the highest spatial resolution for ground-based observations one has to correct for degradations by the Earth's atmosphere. This can be done by on-line and post-facto techniques. Here we combine observations with Adaptive Optics (AO) and speckle reconstruction. As possible techniques we present two modified versions (methods B and C) of the Göttingen speckle masking code and describe their application to observations of a solar active region obtained with the Swedish 1-m Solar Telescope (La Palma) by means of AO. By comparing the results with those obtained from the conventional method (method A), the influence of AO on the post-facto reconstruction is revealed. One has to account for the field dependence of the AO correction and the fitting errors of the calculated surface of the deformable mirror with respect to the according wave fronts. Both new approaches enhance the contrast in the lockpoint region less than the conventional method. Method C uses simulated AO corrected speckle transfer functions (STFs). This method shows the most uniform image quality over the whole field of view and indicates the importance of the atmospheric model assumptions and the partial character of the WF correction by AO with appropriate WF error statistics. However, the consideration of field dependent speckle transfer functions in the classical speckle reconstruction (Method B) can serve as a first approach to avoid an intensity over-amplification around the AO-lockpoint region, although the rms of the contrast in the reconstructed images tends to rise slightly towards the outer parts of the field of view. Even the apparently small differences between the speckle transfer functions, used in the different reconstruction methods, cause the modulus of the estimated intensity differences to vary by up to 22%.
Key words: Sun: photosphere / techniques: high angular resolution / techniques: image processing / instrumentation: adaptive optics
© ESO, 2006
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.