The sky brightness and transparency in i-band at Dome A, Antarctica

TL;DR

This study assesses the sky brightness and atmospheric transparency at Dome A, Antarctica, using 2008 data, revealing generally dark skies suitable for astronomy, with minimal aurorae influence and modeling of celestial contributions.

Contribution

First comprehensive analysis of i-band sky conditions at Dome A, including sky brightness, transparency, and aurorae, based on 2008 observational data.

Findings

Median sky brightness of 20.5 mag arcsec^{-2} during moonless clear nights

No thick clouds observed in 2008 data

Approximately 2% of images affected by strong aurorae

Abstract

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.