Although the use of RGB photometry has exploded in the last decades due to the advent of high-quality and inexpensive digital cameras equipped with Bayer-like colour filter systems, there is surprisingly no catalogue of bright stars that can be used for calibration purposes. Since due to their excessive brightness, accurate enough spectrophotometric measurements of bright stars typically cannot be performed with modern large telescopes, we have employed historical 13-colour medium-narrow-band photometric data, gathered with quite reliable photomultipliers, to fit the spectrum of 1346 bright stars using stellar atmosphere models. This not only constitutes a useful compilation of bright spectrophotometric standards well spread in the celestial sphere, the UCM library of spectrophotometric spectra, but allows the generation of a catalogue of reference RGB magnitudes, with typical random uncertainties ∼0.01 mag. For that purpose, we have defined a new set of spectral sensitivity curves, computed as the median of 28 sets of empirical sensitivity curves from the literature, that can be used to establish a standard RGB photometric system. Conversions between RGB magnitudes computed with any of these sets of empirical RGB curves and those determined with the new standard photometric system are provided. Even though particular RGB measurements from single cameras are not expected to provide extremely accurate photometric data, the repeatability and multiplicity of observations will allow access to a large amount of exploitable data in many astronomical fields, such as the detailed monitoring of light pollution and its impact on the night sky brightness, or the study of meteors, Solar system bodies, variable stars, and transient objects. In addition, the RGB magnitudes presented here make the sky an accessible and free laboratory for the calibration of the cameras themselves.

中文翻译：

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明亮恒星的合成 RGB 光度测量：标准光度系统的定义和分光光度光谱的 UCM 库

尽管由于配备了类似拜耳滤色器系统的高质量和廉价数码相机的出现，RGB 光度测量的使用在过去几十年中呈爆炸式增长，但令人惊讶的是，没有可用于校准目的的亮星目录。由于亮度过高，现代大型望远镜通常无法对明亮恒星进行足够准确的分光光度测量，因此我们使用了历史上的 13 色中窄带光度数据，通过相当可靠的光电倍增管收集，以适应 1346 的光谱使用恒星大气模型的明亮恒星。这不仅构成了在天球中广泛传播的明亮分光光度标准的有用汇编，UCM分光光度光谱库，但允许生成参考 RGB 幅度的目录，典型的随机不确定性约为 0.01 mag。为此，我们定义了一组新的光谱灵敏度曲线，计算为文献中 28 组经验灵敏度曲线的中值，可用于建立标准 RGB 光度系统。提供了使用这些经验 RGB 曲线组中的任何一组计算的 RGB 幅度与使用新的标准光度系统确定的那些之间的转换。尽管来自单个相机的特定 RGB 测量预计不会提供极其准确的光度数据，但观测的可重复性和多样性将允许在许多天文领域访问大量可利用的数据，例如光污染的详细监测及其对夜空亮度的影响，或者对流星、太阳系天体、变星和瞬态物体的研究。此外，此处介绍的 RGB 幅度使天空成为校准相机本身的可访问且免费的实验室。