Optical design of COATLI: an all-sky robotic optical imager with 0.3 arcsec image quality

Abstract

COATLI is a new instrument and telescope that will provide 0.3 arcsec FWHM images from 550 to 920 nm over a large fraction of the sky. It consists of a robotic 50-cm telescope with a diffraction-limited imager. The imager has a steering mirror for fast guiding, a blue channel using a EMCCD from 400 to 550 nm to measure image motion, a red channel using a standard CCD from 550 to 920 nm, and an active optics system based on a deformable mirror to compensate static aberrations in the red channel. Since the telescope is small, fast guiding will provide diffraction-limited image quality in the red channel over a large fraction of the sky, even in relatively poor seeing. COATLI will be installed at the Observatorio Astronomico Nacional in Baja California, Mexico, in September 2016 and will operate initially with a simple interim imager. The definitive COATLI instrument will be installed in 2017. In this paper, we present some of the details of the optical design of the instrument.