A wide field corrector with loss-less and purely passive atmospheric dispersion correction

TL;DR

This paper presents a passive, gravity-driven wide field corrector lens system for the VISTA telescope that corrects atmospheric dispersion without active components, simplifying operation and maintenance.

Contribution

It introduces a novel passive atmospheric dispersion correction method using a gravity-driven lens element in a wide field corrector for large telescopes.

Findings

Achieves 2.5-degree field correction for VISTA telescope

Uses a single, laterally displaced lens element for ADC

Operates without motors, encoders, or software control

Abstract

A 2.5 degree field diameter corrector lens design for the Cassegrain focus of the VISTA 4 meter telescope is presented. It comprises four single elements of glasses with high UV transmission, all axi-symmetric for operation at the zenith. One element is displaced laterally to provide atmospheric dispersion correction. A key feature, especially beneficial for the VISTA application, is that the ADC element can be mounted so it is driven simply by gravity; thus its operation needs no motors, encoders, cabling, or software control. A simple mechanical design to achieve this and the optical performance details are described.