The Wendelstein three channel imager (3KK): alignment, commissioning, and first results

Abstract

The Ludwig-Maximilians-Universität München operates an astrophysical observatory on the summit of Mt. Wendelstein which was equipped with a modern 2m-class robotic telescope in 2011^1-3. One of the two Nasmyth ports is designed to deliver the excellent (< 0.8” median) seeing of the site for a FoV of 60 arcmin² without any corrector optics at optical and near infrared (NIR) wavebands. This port hosts a three channel imager whose design was already presented in Lang-Bardl et al. 2010.⁴ It is designed to efficiently support observations of targets of opportunities like Gamma-Ray-bursts or efficient photometric redshift determination of sources identified by surveys like PanSTARS, Planck (SZ) or eROSITA. The covered wavelength range is 340 nm to 2.3 microns. The camera provides standard broadband filters (Sloan, Y, J, H, Ks) and 5 narrowband filters (OI, Hα, SII, H₂, Br_λ). The narrowband filters will enable deep studies of star forming regions. We present the final design of the camera, the assembly and alignment procedure performed in the laboratory before we transported the instrument to the observatory. We also show first results of the achieved on sky performance concerning image quality and efficiency of the camera in the different filter passbands.