Summary: | The summit of the Antarctic plateau, Dome A, is proving to be an excellent site for optical, near-infrared, and terahertz astronomical observations. Gattini is a wide-field camera installed on the PLATO instrument module as part of the Chinese-led traverse to Dome A in 2009 January. We present here the measurements of sky brightness with the Gattini ultra-large field of view (90° x 90°) in the photometric B-, V-, and R-bands; cloud cover statistics measured during the 2009 winter season; and an estimate of the sky transparency. A cumulative probability distribution indicates that the darkest 10% of the nights at Dome A have sky brightness of S_B = 22.98, S V = 21.86, and S_R = 21.68 mag arcsec^(−2). These values were obtained during the year 2009 with minimum aurora, and they are comparable to the faintest sky brightness at Maunakea and the best sites of northern Chile. Since every filter includes strong auroral lines that effectively contaminate the sky brightness measurements, for instruments working around the auroral lines, either with custom filters or with high spectral resolution instruments, these values could be easily obtained on a more routine basis. In addition, we present example light curves for bright targets to emphasize the unprecedented observational window function available from this ground-based site. These light curves will be published in a future paper. © 2017 The American Astronomical Society. Received 2016 October 30; revised 2017 May 13; accepted 2017 May 15; published 2017 June 13. We thank Shri Kulkarni and Caltech Optical Observatories, Gerard Van Belle, and Chas Beichman for their financial contributions to this project. We are grateful to Xiaofeng Wang, Chao Wu, Ming Yang, Tianmeng Zhang, Yanping Zhang, and Jilin Zhou for helpful discussions. This research is supported by the Chinese PANDA International Polar Year project and the Polar Research Institute of China. The project was funded by the following awards from the National Science Foundation Office of Polar Programs: ...
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