Compensating for Differential Atmospheric Refraction in the W. M. Keck Observatory Adaptive Optics System

摘要

Differential Atmospheric Refraction (DAR) reduces image quality on ground-based 10-m telescopes equipped with Adaptive Optics (AO). Particularly affected are the long exposure data taken in narrow-band imaging or spectroscopic mode. The magnitude of the DAR is a function of the effective wavelength of the wavefront sensor detector, meteorological variables, the observing wavelength and the elevation of the observation. In this paper, we present the approach taken by the Keck Adaptive Optics team to compensate for DAR during AO observing. This paper will present a description and illustration of the problem and our solution to it, including some implementation details. This paper also presents some tips on observing techniques, along with some details on current performance, a description of the issues limiting the performance, and our plans for the future.