Mechanical design of the WIYN One Degree Imager (ODI)

The WIYN consortium is building the One Degree Imager (ODI) to be mounted to a Nasmyth port of the WIYN 3.5m telescope, located at Kitt Peak, Arizona (USA). ODI will utilize both the excellent image quality and the one-degree field of view that the telescope delivers. To accommodate the large field of view (~0.39m diameter unvignetted field with 0.54m across the diagonal of the one-degree-square, partially vignetted field), 0.6m-class optics are required. The ODI design consists of a two element corrector: one serves as a vacuum barrier to the cryostat, the other is an asphere; two independently rotating bonded prism pairs for atmospheric dispersion compensation (ADC); nine independently deployable filters via a simple pivoting motion; and a 971 mega-pixel focal plane consisting of 64 orthogonal transfer array (OTA) devices. This paper is an overview of the mechanical design of ODI and describes the optical element mounting and alignment strategy, the ADC & filter mechanisms, plus the focal plane. Additionally, the project status will be discussed. In accompanying papers Jacoby1 describes ODI's optical design, Yeatts2 describes the software and control system design, and Harbeck3 gives a general update on the project.