| Summary: | The i-band observing conditions at Dome A on the Antarctic plateau have been investigated using data acquired during 2008 with the Chinese Small Telescope Array. The sky brightness, variations in atmospheric transparency, cloud cover, and the presence of aurorae are obtained from these images. The median sky brightness of moonless clear nights is 20.5 mag arcsec^(–2) in the SDSS i band at the south celestial pole (which includes a contribution of about 0.06 mag from diffuse Galactic light). The median over all Moon phases in the Antarctic winter is about 19.8 mag arcsec^(–2). There were no thick clouds in 2008. We model contributions of the Sun and the Moon to the sky background to obtain the relationship between the sky brightness and transparency. Aurorae are identified by comparing the observed sky brightness to the sky brightness expected from this model. About 2% of the images are affected by relatively strong aurorae. © 2010 The American Astronomical Society. Received 2009 December 2; accepted 2010 June 19; published 2010 July 12. This study has been supported by the Chinese National Natural Science Foundation through grants 10873016, 10803007, 10473012, 10573020, 10633020, 10673012, and 10603006, and by the National Basic Research Program of China (973 Program), No. 2007CB815403. This research is also supported by the Chinese PANDA International Polar Year project and the Polar Research Institute of China (PRIC). The support of the Australian Research Council and the Australian Antarctic Division for the PLATO observatory is gratefully acknowledged. The authors thank all members of the 2008 and 2009 PRIC Dome A expeditions for their heroic effort in reaching the site and for providing invaluable assistance to the expedition astronomers in setting up and servicing the PLATO observatory and its associated instrument suite. Iridium communications were provided by the US National Science Foundation and the United States Antarctic Program. Additional financial contributions have been made by the ...
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