Scientific performance analysis of the SYZ telescope design vs. the RC telescope design

Abstract

Recently, Su et al. (2016) propose a telescope design, referred as the "SYZ" design, for Chinese new project of a 12m optical-infrared telescope. The SYZ telescope design consists of three aspheric mirrors with non-zero power, including a relay mirror below the primary mirror. SYZ design yields a good imaging quality and has a relatively flat field curvature at Nasmyth focus. To evaluate the science-compatibility of this three-mirror telescope, in this paper, we thoroughly compare the performance of SYZ design with that of Ritchey-Chr\'etien (RC) design, a conventional two-mirror telescope design. Further, we propose the Observing Information Throughput ($OIT$) as a metric for quantitatively evaluating the telescopes' science performance. We find that although a SYZ telescope yields a superb imaging quality over a large field of view, a two-mirror (RC) telescope design holds a higher overall throughput, a better diffraction-limited imaging quality in the central field of view (FOV$<5'$) which is better for the performance of extreme Adaptive Optics (AO), and a generally better scientific performance with a higher $OIT$ value.