A new broad-band atmospheric dispersion corrector for HROS-TMT

Abstract

Atmospheric dispersion causes light from celestial objects with different wavelengths to refract at varying angles as it passes through Earth’s atmosphere. This effect results in an elongated image at the focal plane of a telescope and diminishes fibre coupling efficiency into spectrographs. We propose an optical design that incorporates a Rotational Atmospheric Dispersion Corrector (RADC) to address the broad-band dispersion for the multi-object mode of the High-Resolution Optical Spectrograph (HROS) on the Thirty Meter Telescope (TMT). The RADC corrects the dispersion across the entire wavelength range (0.31–1 μm), using Amici prisms optimized for over 90 per cent transmission efficiency and minimal angular deviation of the beam from the optical axis after dispersion correction. For enhanced accuracy, particularly in the blue region, we have, for the first time, implemented the Filippenko model in Zemax via a custom Dynamic-Link Library (DLL) file.