<title>Design of a collimator support to provide flexure control on Cassegrain spectrographs</title>

Abstract

The Echellette Spectrograph and Imager (ESI) is being built at UCO/Lick Observatory for the Cassegrain focus of the Keck II telescope. The collimator mirror is optimally constrained by a space-frame structure. It will be actively moved to provide the focus and flexure (tip and tilt) control for the instrument. Careful attention to space-frame geometry has simplified the mechanical design. Analytical and Finite Element Analysis (FEA) are presented to demonstrate how a simple but very stiff structure is used to provide support, flexure control, and focus.