A High Resolution Spectrograph for the 72 cm Waltz Telescope at Landessternwarte, Heidelberg

TL;DR

The paper presents the design and initial on-sky results of the Waltz Spectrograph, a high-resolution instrument aimed at detecting exoplanets through precise radial velocity measurements with a 72 cm telescope.

Contribution

It introduces a novel high-resolution spectrograph optimized for exoplanet detection, featuring a specific optical design and stabilization techniques for high radial velocity precision.

Findings

Spectral resolving power of R~65,000 achieved

Radial velocity precision better than 5 m/s targeted

Initial on-sky tests demonstrate instrument capability

Abstract

The Waltz Spectrograph is a fiber-fed high-resolution \'echelle spectrograph for the 72 cm Waltz Telescope at the Landessternwarte, Heidelberg. It uses a 31.6 lines/mm 63.5$^{\circ}$ blaze angle \'echelle grating in white-pupil configuration, providing a spectral resolving power of $R\sim$65,000 covering the spectral range between 450$-$800\,nm in one CCD exposure. A prism is used for cross-dispersion of \'echelle orders. The spectrum is focused by a commercial apochromat onto a 2k$\times$2k CCD detector with 13.5$\mu$m per pixel. An exposure meter will be used to obtain precise photon-weighted midpoints of observations, which will be used in the computation of the barycentric corrections of measured radial velocities. A stabilized, newly designed iodine cell is employed for measuring radial velocities with high precision. Our goal is to reach a radial velocity precision of better than 5 m/s, providing an instrument with sufficient precision and sensitivity for the discovery of giant exoplanets. Here we describe the design of the Waltz spectrograph and early on-sky results.