Enhanced Seeing Mode at the Large Binocular Telescope Observatory

The SOUL Adaptive Optics System at the Large Binocular Telescope Observatory (LBTO), in conjunction with the f/30 camera on the LUCI (LBT Utility Camera in the Infrared) instruments, delivers diffraction-limited image quality with a 30"x30" field of view. Full AO offers diffraction limited correction with up to 500 modes but the anisoplanitism effects limit the usable field of view. The AO system also includes a low-mode form delivering only 11 modes of correction (including fast tip and tilt corrections) to remove jitter and residual aberrations. This low-mode form of operation is referred to as Enhanced Seeing mode (ESM) and is found to consistently provide significant, uniform, angular correction across the full 4'x4' field of view of the wide field f/3.75 camera on the LUCI instruments. ESM is utilized at the LBTO in two regimes to improve over seeing limited operations. ESM can achieve a uniform angular resolution of 0.22" across the full field of view in the best conditions. It offers the opportunity to improve both the angular and spectral resolution of the long-slit and multi-object spectroscopy (MOS) by improving the signal-to-noise and allowing for smaller slit widths. In mediocre or poor natural seeing, users can broaden their conditional constraints. ESM allows users to achieve the desired resolution with a natural seeing that would otherwise provide unsuitable results. In poor to mediocre seeing (1.5-2") the delivered image quality in terms of full width half maximum is improved by a factor of similar to 2. Many strides have been made to improve the efficiency and characterize this mode of operation in various conditions. It has been proposed that Enhanced Seeing Mode should become a standard observational mode for the near-infrared LBTO observations when an AO reference star is available.