Optical Surfaces has delivered a pair of ultra-high precison counter-rotating doublet prisms for the atmospheric dispersion corrector (ADC), a key element in instruments deployed by the Song project.
The Song project is a collaboration between scientists at the Department of Physics and Astronomy, University of Aarhus, and the Niels Bohr Institute, University of Copenhagen.
Song stands for Stellar Observations Network Group and the purpose of the project is to design an observatory that consists of a network of telescopes distributed around the planet.
The design of the Song telescope will target two scientific purposes: it must measure stellar oscillations that can probe the internal structure of stars and be able to find Earth-like planets in the Milky Way.
Song will consist of a network of 1m class telescopes distributed worldwide for measurement of stellar oscillations and planet detection via microlensing events.
The prototype telescope and instrument suite is currently being designed.
Two Lucky Imaging cameras, observing in the Vis and Red bands, are situated at the Nasmyth focal station.
Via a Coude train, an f/37 beam can be fed to a high-resolution spectrograph.
In order to deliver diffraction-limited performance, which is especially important for the observations in the Vis and Red bands with zenith distances of as much as 70deg, an atmospheric dispersion corrector (ADC) was required.
The ADC consists of a pair of counter-rotating doublet prisms placed approximately 75cm before the focal plane, in the combined Vis/Red band.
Optical Surfaces produced two identical glass prisms of 45mm diameter with a surface accuracy of lambda/20 p-v and micro roughness of better than 1nm rms to provide the diffraction-limited performance required by the Song project team.
