Development of image motion compensation system for 1.3m telescope at Vainu Bappu Observatory

We developed a tip-tilt system to compensate the turbulence induced image motion for the 1.3 m telescope at Vainu Bappu Observatory, at Kavalur. The instrument is designed to operate at the visible wavelength band (480 − 700 nm) with a field of view of 1' × 1'. The tilt corrected images have demonstrated up to ≈ 57% improvement in image resolution and a corresponding peak intensity increase by a factor of ≈ 2.8. A closed-loop correction bandwidth of ≈ 26 Hz has been achieved with on-sky tests and the root mean square motion of the star image has been reduced by a factor of ~ 14. These results are consistent with theoretical and numerical predictions of wave-front aberrations caused by atmospheric turbulence and image quality improvement expected from a real-time control system. In this paper, we present details of the instrument design, laboratory calibration studies and quantify its performance on the telescope.