SIGHT: the Palomar 5m telescope LGS AO system maximizing visible-light spectroscopic sensitivity

SIGHT is a new approach to adaptive optics emphasizing panchromatic image sharpening from 360 nm – 2500 nm with specific intent to increase spectrograph observing sensitivity and operational efficiency. Utilizing a single, pilot-safe ultraviolet (invisible) Rayleigh laser guide star (LGS), we prioritize all-sky seeing enhancement and energy concentration, with minimal observing overheads, over absolute spatial resolution. We accomplish this by releasing the system requirement for natural guide star (NGS) tip-tilt wavefront sensing, seeking instead partial tip-tilt information obtainable with LGS telemetry alone. By implementing an ultra-compact (17 cm x 20 cm x 56 cm) parfocal AO relay installed permanently ahead of the Cassegrain focus, we enable high-spatial-frequency AO correction over a field of view of up to 30 arcseconds in diameter. The development of AO differentiated for specific scientific goals represents a further maturation of AO technology beyond the gilded cage of Strehl ratio