适于天文台夜天光亮度测量的小视场高灵敏度光电亮度测量技术

It has been said that existing and potential optical astronomical sites are suffering from the impacts of light pollution with the rapid development of civil lighting. However, the investigation and study of light pollution is still in blank field in the country. It is essential to build and accumulate data of night-sky brightness for reducing light pollution and protecting astronomical sites. In order to measure night-sky brightness in site surveys and monitor the change of night-sky brightness at astronomical sites, a night-sky brightness meter employing a photomultiplier tube as the detector is proposed. It is designed to measure the absolute luminance of night sky directly and be well suited for astronomiacal surveys. With strict correction of spectral responsivity, unique optical design, precise circuits and signal processing, the instrument holds promise for achieving high sensitivity with the minimum solution of 10^-6 cd/m^2(equivalent to 27.4 mag/arcsec^2) to insure faint luminance measurement efficiently and reliably. Measuring directly the absolute luminance of night sky, this technogy will be a viable alternative to the classical method using a telescope and a CCD camera。It does not need to involve time of telescopes and suits that role better in mobile filed measurements. More importantly, measurement results of photoelectric luminance meters can be traceable to national standards of luminance after exact calibration. When they are applied in various sites, good consistence among them helps to make transverse and longitudinal comparisons.

随着城市照明的高速发展，光污染对现有和潜在的光学天文台的影响越来越严重。而国内对光污染的调查研究尚处于起步阶段，建立夜天光亮度测量手段和积累长期监测数据是“减少光污染、保护天文台”的基础性工作。为便于天文选址中的夜天光亮度测量和现有台站的夜天光亮度长期监测，提出以光电倍增管作为探测器，设计和研制一种适于天文工作需要的、直接测量夜天光亮度的便携式光电亮度计。亮度计通过严格光谱响应匹配以符合绝对亮度测量要求，并采用独特光学设计，配合精密电路和信号处理，小视场下灵敏度最小分辨达到10^-6cd/m^2(相当于27.4mag/arcsec^2)，确保微弱亮度测量的准确有效。与传统方法(望远镜加CCD照相机)相比，光电亮度技术的优越性在于测量简单快捷、不依赖望远镜、适合野外流动性测量。且多台光电亮度计严格定标后均能溯源至国家亮度标准，应用于各天文台时，良好的一致性便于天文台天光背景的横、纵向比较。

夜天光亮度是评价一个天文台台址质量的重要参数之一，是衡量光污染的直接指标。随着光污染问题日益突出，开展一种有效的夜天光亮度测量技术研究，是对当前测量方法的有效补充。本项目采用光电倍增管作为探测器，设计和研制了一种适于天文工作需要的、直接测量夜天光亮度的便携式光电亮度计。亮度计视场为2度，分辨力达到10^-6cd/m^2(相当于27.4mag/arcsec^2)，保证了夜天空微弱亮度测量的准确有效。仪器通过实验测试均取得了良好的性能指标，与望远镜加CCD测量方法相比，其优越性在于测量简单快捷、不依赖望远镜、适合野外流动性测量。本项目研究成果能够有效用于天文选址中的夜天光亮度测量和现有台站的夜天光亮度长期监测，为防治光污染和保护天文台提供国产化手段。