Feasibility study of an absolute energy calibration atmospheric Cherenkov telescopes by starlight

A new method is presented for an absolute energy calibration of imaging atm ospheric Cherenkov telescopes as a whole instrument at all relevant wavelen gths. For this study the Cherenkov telescope #1 of the HEGRA(1) experiment was used. The calibration was carried out by detecting the light of differe nt selected stars during one night. From the data a simple linear correlati on was derived between the anode current of the Cherenkov camera photomulti plier tubes and the incident photon flux. This result is important for the imaging air Cherenkov technique in several aspects: The method enables to d etermine the response function of Cherenkov telescopes in the energetic ran ge of Cherenkov light quickly and reliably. Therefore it can be used as an atmospheric calorimeter by measuring the absolute integrated flux of Cheren kov photons. Moreover, the signal of a point run can be predicted and a sim ulation of the apparatus response can be carried out more reliably.