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As telescopes dramatically increase in aperture, the size and complexity of instrumentation also increases dramatically. Simply scaling up existing spectrograph designs may not be feasible and new approaches must be considered. One alternate approach is multiplexing, where the high cost of large optics is replaced by smaller, lower-cost optics albeit in higher quantities. While the idea of large-scale multiplexed instruments is not new, ELTs push the scaling of instruments into territory where multiplexing may have significant advantages. However, it remains to be seen if optical mounts can be made to meet the ever-tightening optical requirements of modern instruments while retaining the low-cost and ease of use required to make multiplexing a feasible approach.
This paper details the design, prototyping and testing of several types of low-cost semi-kinematic optical mounts at NRCHerzberg from a practical standpoint. Optical mounts tested cover a range of types intended to be easy to manufacture, quick to assemble and suitable for various instrument environments. Assembly repeatability in tip/tilt/focus, assembly time, and wavefront error due to stress birefringence (simulated) are quantified and results presented. Thermal stability, suitability for use in cryogenic environments and ease of manufacture/assembly are also analyzed. Various qualitative metrics are also discussed. Quantitative and qualitative metrics are discussed and presented in a design table to aid in directly comparing lens mounting concepts. Results are also interpreted to determine the direction of future R&D efforts towards creating large-scale, multiplexed instruments.
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