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10 July 2008 Assessment of local seeing within a telescope lab environment
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Abstract
Turbulence, which may exist along an optical path inside a telescope or laboratory setup such as the Dunn Solar Telescope observing room, can negatively impact the imaging performance at the final detector plane. In order to derive requirements and error budget terms for the Advanced Technology Solar Telescope (ATST) we performed interferometric measurements with the goal to determine the amount of aberrations introduced by the air mass through which the beam propagates and characterize temporal and spatial frequencies of these aberrations. We used a He-Ne laser interferometer to measure aberrations along a 50m and 33m, collimated 150mm diameter laser beam. The experiments were performed with both vertical and horizontal beam propagation. We investigated the impact on the amount of self-induced turbulence of the difference in temperature between the top and the bottom of the optical laboratory, the impact of heat sources, such as electronics racks, and the effect of a laminar air flow applied to parts of the beam path. The analysis of the interferograms yields values of the rms wave front aberrations excluding tip/tilt in the range of 1.45nm/m - 2nm/m (@632nm) for the vertical beam propagation and between 0.8nm/m - 1.6nm/m for the horizontal beam. The spatial spectrum of the turbulence tends to decay faster than Kolmogorov turbulence. This is true, in particular, for the horizontal beam path. The temporal frequencies are on the order of a few Hz (<10Hz).
© (2008) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Rudolph Biérent, Thomas Rimmele, and Jose Marino "Assessment of local seeing within a telescope lab environment", Proc. SPIE 7012, Ground-based and Airborne Telescopes II, 701234 (10 July 2008); https://doi.org/10.1117/12.788046
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