Читать книгу The Doppler Method for the Detection of Exoplanets - Professor Artie Hatzes - Страница 29

For photon statistics, the uncertainty in the detected photons, N_p, is σ=Np. The S/N is simply S/N=Np/σ=NpNp=Np. So, for astronomical observations, the important quantity is the number of detected photons. However, CCD pixel values are ADUs, which are related to the actual number of photons through the gain factor (G), Np=GNp. When using a CCD for the first time, it is wise to check the gain factor and not merely rely on documentation or information in the headers of the observations as these may be outdated. The CCD gain can be easily measured using either of two methods.