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W. R. Brown, D. G. Fabricant, D. A. Boyd (Harvard-Smithsonian Center for Astrophysics)
We present a detailed thermal study of Binospec, a wide-field, multi-slit spectrograph being developed for use at the converted MMT. Modern astronomical instruments that use high performance refractive optics can be quite sensitive to temperature changes and thermal gradients. This sensitivity arises from thermal expansion of the lenses and lens mounts, as well as changes in refractive indices with temperature. Thermally induced tilts and decenters of optical elements are also of concern. Binospec's optics are designed to maintain image quality, image scale, and focus over a wide temperature range, but they must remain approximately isothermal to attain this performance.
We use finite element modeling techniques to assess the impact of the continually changing thermal environment upon the Cassegrain-mounted Binospec spectrograph. The thermal models consider the effects of conduction, convection, and radiation. We have checked our results using simple test cases that can be verified analytically, and have made detailed models of several components to test the required level of model fidelity. We describe significant model conclusions and the design recommendations that result from them.
The author(s) of this abstract have provided an email address for comments about the abstract: wbrown@cfa.harvard.edu