Echelle spectrographs for 8-m class telescopes

The modifications required to construct an echelle spectrograph similar to the UCLES (currently in use on the 3.9-m AAT and described by Walker et al., 1986) for an 8-m-class telescope are discussed in detail and illustrated with diagrams. The design and operational parameters of the UCLES are reviewed, and a direct factor-of-two linear scaling of the UCLES for an 8-m telescope is outlined, with particular attention to a mosaicked CCD detector array and echelle configuration, the relationship between the field rotation problem and the telescope secondary focus ratio, the feasibility of a Littrow layout with prisms in double pass immediately ahead of the echelle, prism mosaics as a low-cost approach to prismatic cross-dispersion, the characteristics and application of the 79 g/mm R4 echelle, and the possible use of white-light pupil imaging, as proposed by Baranne (1972).