3kk: the Optical-NIR Multi-Channel Nasmyth Imager for the Wendelstein Fraunhofer Telescope

Abstract

The Ludwig-Maximilians-Universit¨at M¨unchen operates an astrophysical observatory on the summit of Mt. Wendelstein1 which will be equipped with a modern 2m-class, robotic telescope.² One Nasmyth port of the new Fraunhofer telescope is designed to deliver the excellent (< 0.8" median) seeing of the site [1, Fig. 1] for a smaller FoV of 60 arcmin2 without any corrector optics at optical and NIR wavebands. Thus, it will be optimized for fast multi-wavelength follow-up observations of targets of opportunities (e.g. Gamma-Ray-bursts) or efficient photometric redshift determinations of huge numbers of galaxy clusters identified in optical (PanSTARRS), SZ (Planck) or X-ray (eROSITA) surveys. We present the design of a compact 3 channel camera which serves these science requirements, built partly from commercially available Fairchild-2k optical CCD³ cameras (Apogee), coupled with small Bonn Shutters,⁴ and mounted on commercial high precision linear stages for differential focusing. A specially designed beam-splitter system maintains the high optical quality. The NIR camera is built in cooperation with the Institute for Astronomy in Hawaii. The combined operation of this camera with two spectrographs at the same telescope port has already been presented at SPIE 2008.⁵