Clear widens the field for observations of the Sun with multi-conjugate adaptive optics^⋆

¹ National Solar Observatory, 3665 Discovery Drive, Boulder, CO 80303, USA
e-mail: dschmidt@nso.edu
² Big Bear Solar Observatory, New Jersey Institute of Technology, 40386 North Shore Lane, Big Bear City, CA 92314, USA
³ Kiepenheuer-Institut für Sonnenphysik, Schöneckstraße 6, 79104 Freiburg, Germany
⁴ Large Binocular Telescope Observatory, 933 North Cherry Avenue, Tucson, AZ 85721, USA
⁵ Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611, Australia

Received: 27 October 2016
Accepted: 10 December 2016

Abstract

The multi-conjugate adaptive optics (MCAO) pathfinder Clear on the New Solar Telescope in Big Bear Lake has provided the first-ever MCAO-corrected observations of the Sun that show a clearly and visibly widened corrected field of view compared to quasi-simultaneous observations with classical adaptive optics (CAO) correction. Clear simultaneously uses three deformable mirrors, each conjugated to a different altitude, to compensate for atmospheric turbulence. While the MCAO correction was most effective over an angle that is approximately three times wider than the angle that was corrected by CAO, the full 53′′ field of view did benefit from MCAO correction. We further demonstrate that ground-layer-only correction is attractive for solar observations as a complementary flavor of adaptive optics for observational programs that require homogenous seeing improvement over a wide field rather than diffraction-limited resolution. We show illustrative images of solar granulation and of a sunspot obtained on different days in July 2016, and present a brief quantitative analysis of the generalized Fried parameters of the images.