Wide-Field Image Restoration of G-Band and Ca ii K Images Containing Large and Complex Active Regions

Abstract

Restoration of solar images to achieve near diffraction-limited spatial resolution is commonly implemented on large-aperture solar telescopes. However, the extent of the restored field-of-view is typically only 100′′ or even smaller. This study reports on wide-field image restoration of G-band and Ca ii K images obtained with the 0.7-meter Vacuum Tower Telescope (VTT) at Observatorio del Teide, Tenerife, Spain. The Kiepenheuer Adaptive Optics System (KAOS) at the VTT provides a field-of-view with a diameter of 270′′. Time series of datasets with 100 images were acquired with a large-format (7920 × 6004 pixels) CMOS imager at a frame rate of 30 Hz. An experimental optical setup that enabled wide-field imaging is briefly presented. Results from speckle-masking imaging and Multi-Frame Blind Deconvolution (MFBD) demonstrate the unique potential of the VTT for wide-field imaging. Power spectral analysis quantifies the instrument performance as a function of time and with distance from the lock point of the AO system. Further science capabilities are established using Local Correlation Tracking (LCT), Background-subtracted Solar Activity Maps (BaSAMs), and image quality/seeing metrics. In summary, commercial off-the-shelf camera systems can become an asset to sub-meter-class solar telescopes and open up new science opportunities at the interface between large-aperture and synoptic solar telescopes.