格雷厄姆山的天空表面亮度：用大型双目望远镜进行的UBVRI科学观测
Sky Surface Brightness at Mount Graham: UBVRI Science Observations with the Large Binocular Telescope
摘要：
本文介绍了在大双目望远镜（LBT）上进行的第一次双目模式科学运行中获得的格雷厄姆山国际天文台的天空表面亮度测量结果。我们的数据质量评估程序分析了2008年2月至2008年6月期间的23个无月的夜晚，共860张图像。这些在太阳活动极小期拍摄的数据显示，格雷厄姆山在光度条件下仍然拥有最黑暗的天空之一，与其他一流的天文台竞争。经天顶校正后，U、B、V R和I的值分别为21.98、22.81、21.81、20.82和19.78 mag/arcsec ^2。在测光条件下，朝向图森和凤凰城观测时，天空背景比中值高约0.1 mag/arcsec^2，但在非测光条件下，天空背景可能高出约0.5 mag/arcsec^2。格雷厄姆山的天空在大气质量约为1.4时比天顶亮约0.32等/角秒^[2]，但没有发现随夜晚时间变化的明显趋势。我们首次证明了格雷厄姆山的天空背景对太阳活动的依赖性。事实上，在2008年，在B和V波段，天空比1999 ~ 2002年暗了约0.3等/角秒^[2]。根据这些结果，我们得出结论，格雷厄姆山仍然是一个一流的观测点，与夏威夷，智利和加那利群岛最黑暗的地方相媲美。
英文摘要：
We present the measurements of sky surface brightness on Mount Graham International Observatory obtained during the first binocular-mode science runs at the Large Binocular Telescope (LBT). A total of 860 images obtained on 23 moonless nights in the period Feb 2008-Jun 2008 were analyzed with our data quality assessment procedure. These data, taken at the solar minimum, show that Mt.Graham, in photometric conditions, still has one of the darkest skies, competing with the other first-class observatories. The zenith-corrected values are 21.98, 22.81, 21.81, 20.82 and 19.78 mag/arcsec^2 in U, B, V R and I, respectively. In photometric conditions, the sky background is ~0.1 mag/arcsec^2 higher than the median when observing toward Tucson and Phoenix but it may be up to ~0.5 mag/arcsec^2 higher in non-photometric conditions. The sky at Mt.Graham is ~0.32 mag/arcsec^2 brighter at airmass ~1.4 than at zenith but no significant trend was found with the time of the night. We demonstrated the dependence of the sky background at Mt.Graham on the solar activity for the first time. In fact in 2008, at B and V bands, the sky was ~0.3 mag /arcsec^2 darker than in 1999-2002. With these results we conclude that Mt.Graham is still a first-class observing site, comparable to the darkest sites in Hawaii, Chile and Canary Islands.
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