Optical Sky Brightness and Transparency During the Winter Season at Dome A Antarctica From the Gattini-Allsky Camera

TL;DR

This study measures sky brightness, cloud cover, and transparency at Dome A, Antarctica, demonstrating its suitability for optical astronomy with exceptionally dark skies and excellent observational conditions during winter.

Contribution

First comprehensive measurements of sky brightness, cloud cover, and transparency at Dome A using the Gattini camera, highlighting its potential as a premier astronomical site.

Findings

Darkest 10% of nights have sky brightness comparable to Mauna Kea

Sky brightness values around 22 mag arcsec^{-2} in B-band

Cloud cover and transparency data support optimal observing conditions

Abstract

The summit of the Antarctic plateau, Dome A, is proving to be an excellent site for optical, NIR, and THz astronomical observations. GATTINI was a wide-field camera installed on the PLATO instrument module as part of the Chinese-led traverse to Dome A in January, 2009. We present here the measurements of sky brightness with the Gattini ultra-large field of view (90 deg x 90 deg) 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 around the year 2009 with minimum aurora, and they are comparable to the faintest sky brightness at Mauna Kea 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.