High-Resolution Imaging at the SOAR Telescope

Bright single and binary stars were observed at the 4.1 m telescope with a fast electron-multiplication camera in the regime of partial turbulence correction by the visible-light adaptive optics system. We compare the angular resolution achieved by simple averaging of AO-corrected images (long-exposure), selection and recentering (shift-and-add or "lucky" imaging), and speckle interferometry. The effect of partial AO correction, vibrations, and image postprocessing on the attained resolution is shown. Potential usefulness of these techniques is evaluated for reaching the diffraction limit in ground-based optical imaging. Measurements of 75 binary stars obtained during these tests are given and objects of special interest are discussed. We report tentative resolution of the astrometric companion to zeta Aqr B. A concept of advanced high-resolution camera is outlined.