This report presents an cherenkov telescope prototype, observation method of cherenkov light from extensive air showers (EAS)
generated by cosmic rays (CRs) above $10^{16}$eV and preliminary observations. The interest in
cherenkov light differential detectors of EAS is caused by the possibility to measure the depth
of cascade maximum, Xmax, and/or the shower age via angular and temporal distributions of the
cherenkov signal. In particular, it was shown using EAS model simulations that the pulse width
measured at the periphery of the shower, r > 300 m, at sea level is pronouncedly connected with
Xmax. cherenkov detector is a wide-angle telescope working in coincidence with scintillation
detectors, integral and differential cherenkov detectors Yakutsk complex EAS.