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Prospects for Adaptive Optics in the Near IR (1Dec92) (from NSO, NOAO Newsletter No. 32, 1 December 1992) The first experiment for a quantitative assessment of daytime seeing at near infrared (NIR) (1.0-2.2 um) wavelengths was carried out at the NSO/SP Vacuum Tower Telescope in September 1992. The experiment measured: 1) image motion of a bright star (30 Hz) using the VTT's capability of pointing at stars during daytime, 2) solar limb scans (30 Hz), and 3) temporal power spectra (5000 Hz) of angle-of-arrival fluctuations using the solar limb with a Foucault knife-edge test. Various pairs of filters widely separated in wavelength (within the 0.4-2.2 um range) allowed simultaneous measurements in the visible and NIR. Results show markedly smaller image motion in the NIR. Ro (Fried's parameter) followed closely a 6/5 power law with wavelength, as expected from turbulence theory, most of the time. There are, however, also indications that early morning seeing in the NIR is much better than given by this relationship. Ro values as high as 130 cm were measured at 1.6 and 2.2 um, leaving the isoplanatic angle correspondingly large. An implication is that NIR solar adaptive optics systems are favored, as expected, over systems in the visible in terms of simpler and less costly designs. Tron Darvann, Steven Hegwer, Serge Koutchmy, Dick Mann, Fritz Stauffer, Eric Stratton, Larry Wilkins
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