Optical design of a broadband atmospheric dispersion corrector for MAVIS

"The MCAO Assisted Visible Imager and Spectrograph (MAVIS), is a new instrument for ESO’s Very Large Telescope. The science instruments, namely an imager and a spectrograph observing at VIS wavelengths (370-1000nm), are fed by a MCAO module which performs wide field wavefront sensing and correction by means of both NGS and LGS stars. To maximize sky coverage, tip-tilt sensing is done at NIR wavelengths (1000-1700 nm) by selecting up to three stars in a 2arcmin FoV. In order to maximize the stability between NGS wavefront sensor and scientific instruments, we designed a common-path Atmospheric Dispersion Corrector (ADC) able to efficiently compensate for atmospheric differential refraction in the full wavelength range used by the MAVIS sub-systems. In this paper we present the design of the ADC. A few possible combinations of glasses are proposed and compared in terms of residual chromatic aberration, throughput, exit pupil movement and total thickness of the prism assembly."