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In this empirical study, we compare high-resolution observations obtained with the 65-cm vacuum reflector at Big Bear Solar Observatory (BBSO) in 2005 and with the Dunn Solar Telescope (DST) at the National Solar Observatory/Sacramento Peak (NSO/SP) in 2006. We measure the correction of the high-order adaptive optics (AO) systems across the field of view (FOV) using the spectral ratio technique, which is commonly employed in speckle masking imaging, and differential image motion measurements. The AO correction is typically much larger (10 to 25 ) than the isoplanatic angle and can be described by a radially symmetric function with a central core and extended wings. The full-width at half-maximum (FWHM) of the core represents a measure of the AO correction. The average FWHM values for BBSO and NSO/SP are 23.5 and 18.2 , respectively. The extended wings of the function show that the AO systems still contribute to an improved speckle reconstruction at the periphery of the 80 × 80 FOV. The major differences in the level of AO correction between BBSO and NSO/SP can be explained by different contributions of ground-layer-and free-atmosphere-dominated seeing, as well as different FOVs of the wavefront sensors. In addition, we find an anisotropic spectral ratio in sunspot penumbrae caused by the quasi-one-dimensional nature of penumbral filaments, which introduces a significant error in the estimation of the Fourier amplitudes during the image restoration process.

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The New Solar Telescope (NST) project at Big Bear Solar Observatory (BBSO) now has all major contracts for design and fabrication in place and construction of components is well underway. NST is a collaboration between BBSO, the Korean Astronomical Observatory (KAO) and Institute for Astronomy (IfA) at the University of Hawaii. The project will install a 1.6-meter, off-axis telescope at BBSO, replacing a number of older solar telescopes. The NST will be located in a recently refurbished dome on the BBSO causeway, which projects 300 meters into the Big Bear Lake. Recent site surveys have confirmed that BBSO is one of the premier solar observing sites in the world. NST will be uniquely equipped to take advantage of the long periods of excellent seeing common at the lake site. An up-to-date progress report will be presented including an overview of the project and details on the current state of the design. The report provides a detailed description of the optical design, the thermal control of the new dome, the optical support structure, the telescope control systems, active and adaptive optics systems, and the post-focus instrumentation for high-resolution spectro-polarimetry.

The site survey for the Advanced Technology Solar Telescope (ATST) of the National Solar Observatory was initiated in 2002 to find the best location for a 4 m aperture solar telescope. At the end of a 4 year survey, three sites (Big Bear Solar Observatory [BBSO] in California, Mees Solar Observatory [MSO] on Haleakala, Maui, Hawaii, and Observatorio Roque de los Muchachos, on La Palma, Spain) were identified as excellent sites for high-resolution solar observations. MSO was ultimately chosen as the future ATST site. We present a subset of the ATST site survey data, focusing on the local seeing environment at BBSO. In particular, we are interested in the seeing characteristics at a mountain lake-site observatory, its relation to the local environment and climate, and its implications for the 1.6 m New Solar Telescope (NST) currently being built at BBSO. We find a close correlation of very good seeing conditions with the prevailing wind direction and speed. The observatory building, located at the end of a 300 m causeway, is surrounded by the cool waters of Big Bear Lake, which effectively suppress the ground-layer seeing. Very good seeing conditions from sunrise to sunset are a unique feature of BBSO, which makes it ideally suited for synoptic observations and sustained highresolution studies of solar activity and space weather.