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Proceedings Paper

Assessment of local seeing within a telescope lab environment
Author(s): Rudolph Biérent; Thomas Rimmele; Jose Marino
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Paper 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).

Paper Details

Date Published: 10 July 2008
PDF: 9 pages
Proc. SPIE 7012, Ground-based and Airborne Telescopes II, 701234 (10 July 2008); doi: 10.1117/12.788046
Show Author Affiliations
Rudolph Biérent, Ecole Nationale Supérieure de Physique de Grenoble (France)
Thomas Rimmele, National Solar Observatory (United States)
Jose Marino, National Solar Observatory (United States)

Published in SPIE Proceedings Vol. 7012:
Ground-based and Airborne Telescopes II
Larry M. Stepp; Roberto Gilmozzi, Editor(s)

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