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Scintillation-limited photometry with the 20-cm NGTS telescopes at Paranal Observatory

O’Brien, Sean M and Bayliss, Daniel and Osborn, James and Bryant, Edward M and McCormac, James and Wheatley, Peter J and Acton, Jack S and Alves, Douglas R and Anderson, David R and Burleigh, Matthew R and Casewell, Sarah L and Gill, Samuel and Goad, Michael R and Henderson, Beth A and Jackman, James A G and Lendl, Monika and Tilbrook, Rosanna H and Udry, Stéphane and Vines, Jose I and West, Richard G (2022) 'Scintillation-limited photometry with the 20-cm NGTS telescopes at Paranal Observatory.', Monthly Notices of the Royal Astronomical Society, 509 (4). pp. 6111-6118.


Ground-based photometry of bright stars is expected to be limited by atmospheric scintillation, although in practice observations are often limited by other sources of systematic noise. We analyse 122 nights of bright star (Gmag ≲ 11.5) photometry using the 20-cm telescopes of the Next-Generation Transit Survey (NGTS) at the Paranal Observatory in Chile. We compare the noise properties to theoretical noise models and we demonstrate that NGTS photometry of bright stars is indeed limited by atmospheric scintillation. We determine a median scintillation coefficient at the Paranal Observatory of CY=1.54⁠, which is in good agreement with previous results derived from turbulence profiling measurements at the observatory. We find that separate NGTS telescopes make consistent measurements of scintillation when simultaneously monitoring the same field. Using contemporaneous meteorological data, we find that higher wind speeds at the tropopause correlate with a decrease in long-exposure (t = 10 s) scintillation. Hence, the winter months between June and August provide the best conditions for high-precision photometry of bright stars at the Paranal Observatory. This work demonstrates that NGTS photometric data, collected for searching for exoplanets, contains within it a record of the scintillation conditions at Paranal.

Item Type:Article
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Publisher statement:© The Author(s) 2021. Published by Oxford University Press on behalf of Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.
Date accepted:18 November 2021
Date deposited:16 June 2022
Date of first online publication:26 November 2021
Date first made open access:16 June 2022

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