Adaptive optical image compensation experiments on stellar objects

The resolution of a large telescope is limited by various kinds of dynamic wavefront disturbance such as atmospheric turbulence. This has been a problem since the invention of the telescope. An approach for solving the problem is provided by adaptive optical techniques. Compensating for stellar objects in real time is, however, very difficult, because only limited light energy can be used and the temporal-spatial characteristics of dynamic disturbances place very high demands on system specifications. This paper reports the first experiment of a 21-element adaptive optical system for stellar objects on the Yunnan Observatory 1.2-m telescope and presents the improvements of the system for low-light-level stellar objects. The experimental results show that the adaptive optical system can work satisfactorily when the photon counts are as low as 93 per subaperture per integrating time. The experiments show that the effects of adaptive optics in reducing the divergence and wandering of the image spot, in improving resolution, and in increasing image contrast are significant.