Optical Surfaces (Surrey, England) has announced the delivery of a pair of ultra-high-precision counter-rotating doublet prisms for an Atmospheric Dispersion Corrector (ADC), which is part of the SONG (Stellar Observations Network Group) project, a collaboration between scientists at the Department of Physics and Astronomy, University of Aarhus, and the Niels Bohr Institute, University of Copenhagen. The project will measure stellar oscillations that can probe the internal structure of stars and find Earth-like planets in the Milky Way. The 45mm-diameter glass prisms offer a surface accuracy of lambda/20 p-v and microroughness of better than 1nm rms. The ADC will allow observations in the VIS and RED bands with zenith distances of as much as 70°. It consists of a pair of counter-rotating doublet prisms placed approximately 75cm before the focal plane, in the combined VIS/RED band.
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