The 64 Mpixel wide field imager for the Wendelstein 2m Telescope: Design and Calibration

TL;DR

This paper describes the design, calibration, and performance of a 64-megapixel wide-field imager for the Wendelstein 2m Telescope, highlighting its technical specifications and initial on-sky testing results.

Contribution

It presents the detailed design, calibration, and performance evaluation of a novel wide-field imager for the Wendelstein 2m Telescope, including system mechanics, electronics, and detector parameters.

Findings

Good predictability of system throughput from lab measurements

High image quality with median seeing < 0.8"

Successful initial on-sky tests

Abstract

The Wendelstein Observatory of Ludwig Maximilians University of Munich has recently been upgraded with a modern 2m robotic telescope. One Nasmyth port of the telescope has been equipped with a wide-field corrector which preserves the excellent image quality (< 0.8" median seeing) of the site (Hopp et al. 2008) over a field of view of 0.7 degrees diameter. The available field is imaged by an optical imager (WWFI, the Wendelstein Wide Field Imager) built around a customized 2 $\times$ 2 mosaic of 4k $\times$ 4k 15 \mu m e2v CCDs from Spectral Instruments. This paper provides an overview of the design and the WWFI's performance. We summarize the system mechanics (including a structural analysis), the electronics (and its electromagnetic interference (EMI) protection) and the control software. We discuss in detail detector system parameters, i.e. gain and readout noise, quantum efficiency as well as charge transfer efficiency (CTE) and persistent charges. First on sky tests yield overall good predictability of system throughput based on lab measurements.