The adaptive optics simulation and improvement plan of CRAO attached to the 1.3m Araki telescope

Abstract

Compact refractive adaptive optics (CRAO) is a visible compact adaptive optics (AO) system optimized for small telescopes. It was mounted on the 1.3 m Araki telescope of Koyama Astronomical Observatory (KAO) in Kyoto Sangyo University, Japan. CRAO aims to improve the natural seeing 3” to 0.8” at 500 nm at the KAO site. Thus, it needs a large format and highly frequent camera for wide field survey (WFS) and a largely segmented depth map (DM) because the natural seeing ∼3” at the KAO site is especially poor for astronomical observations. To improve the performance of CRAO with a new WFS and DM, we searched for the optimal AO parameters (the number of WFS subapertures (N_WFS), the number of DM actuators (N_DM), and the loop frequency (<i>f</i>_L) with two AO simulators using <i>yao</i> and <i>COMPASS</i>. Consequently, we found that N_WFS &gt; 12×12, N_DM &gt; 80, and <i>f</i>_L &gt; 800 Hz are necessary to achieve the full width at half maximum (FWHM) &lt; 0.8” for point spread function (PSF) under the KAO site’s atmospheric conditions. Finally, we calculated the limiting magnitude (V_lim) with commercially available sensors for WFS and DMs. By combining ORCA-Lightning (Hamamatsu Photonics) and DM97-15 (ALPAO), a deeper limiting magnitude (V_lim ∼ 4.4) can be achieved, even with a 1 m-class telescope.