Abstract

CCD photon counting system represent one of the more efficient technologies in photometric and spectral measurements for stars inside the field of view in ground base observatory, but there are several effects facing observing data through it , so in order to take it into account ,the arriving stellar flux and photon counting rate have been estimated after inserting the expected obstacles in the light path ,using filters system with wide range of stellar magnitudes within the limiting magnitude of the telescope . The tables of photon counting at UBVRI filters for Kitt Peak National Observatory 2.1meter telescope were estimated under the system circumstance and make use of them as indicators for right observation . Key word: CCD photon counting, ground base observatory, stellar flux, limiting magnitude of the telescope