Imaka:. Imaging from Mauna Kea
Résumé
The CFH Telescope has a long history of wide-field imaging, and this is reflected in its users community. Many projects are competing in the A · Omega race but so far, all are limited by atmospheric turbulence. Wisely choosing a site with a very thin ground layer and excellent free-atmosphere seeing would allow very wide fields to be corrected by a GLAO system.1,2 The characteristics of the turbulence of Mauna Kea are perfectly matched to such an instrument making the site an integral part of its design. The goal of this project is to achieve exquisite image quality over the largest possible field of view, with a goal of a FWHM of not more than 0.3" over a square degree field in the optical domain. This goal depends crucially on the thickness of the ground layer and its prevalence. But over such large fields the probability of finding sufficiently numerous and bright natural guide sources is high, although a constellation of laser beacons could be considered to ensure homogeneous and uniform image quality. The image is then limited by the free atmosphere seeing (0.2" to 0.4"). This can be further improved by an Orthogonal Transfer CCD camera (Tonry et al.3) which can correct local image motion on isokinetic scales from residual high altitude tip-tilt. Knowing the vertical turbulence profile, the outer scale and the isokinetic patch plays a critical role at the design level.