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.
@article{arxiv.1407.2193,
title = {A wide field corrector with loss-less and purely passive atmospheric dispersion correction},
author = {Peter Gillingham and Will Saunders},
journal= {arXiv preprint arXiv:1407.2193},
year = {2015}
}