DAG 4m Telescope: on-sky alignment and commissioning

Abstract

The 4-meter class telescope of the Eastern Anatolia Observatory, designed and built by AMOS is a f/14 Ritchey-Chrétien with two Nasmyth foci and active optics system controlling the primary mirror shape and the secondary and tertiary mirrors position. Following the telescope erection on-site and optics integration, the final tests encompassed fine alignment and ultimately performance assessment on-sky. Advanced alignment techniques such as wavefront-curvature sensing and coma-free point adjustment were employed to achieve diffraction-limited performance in optical and near-infrared bands. On-sky tests, complemented by lucky-imaging methods, confirmed excellent image quality. This paper details the on-site installation steps, alignment procedures, and final performance results, demonstrating the readiness of the DAG telescope for scientific operations.