Squash: a slit spectrograph with no moving parts

Abstract

The Liverpool Telescope (LT) is a 2-metre fully autonomous telescope sited on La Palma. It is primarily used in time-domain astrophysics, as such, there is a requirement for rapid response and high-efficiency observation and instrumentation. To reduce maintenance requirements and increase reliability we are developing a spectrograph (Squash) with no moving parts for use on the LT. The primary design feature is a beam splitter where a small fraction of light will be reflected towards a dedicated acquisition detector. The rest of the light will pass through the system for spectroscopy with a second detector. We present a design for the Squash spectrograph with a dichroic (8000-Å cut off), sCMOS (shutterless) cameras, long slit with 1.8 arcsec width on sky, VPH grating, off axis parabolic mirror collimator, resolution R ∼750 and wavelength range 3700-7400Å.