The observation of OTs connected to GRBs seems to have confirmed the cosmological hypothesis. However, a detailed knowledge of the source behavior in different spectral bands, with high time resolution and maximum possible bandwidth, before and during the GRB emission is necessary to understand the nature of these sources. In order to obtain this goal, the use of very large, wide fieldbadmirrors is proposed and justified. The dependence of detection limits from size, beam aperture, transparency, background level, time exposition, and detector quantum efficiency are considered for huge Cˇerenkov telescopes; the possibility of a contemporaneous observation in the optical band and in the VHE band with the same mirror, by using two different mirror/detector configurations, is suggested. ©2000 American Institute of Physics.