The Perugia variability monitoring of blazars

In fifteen years of optical monitoring performed with the 0.4m automatic imaging telescope (AIT) of the Perugia University Observatory, more than 35000 VRI (and a few B) photometric data points were collected, contributing to get an important database of the multi-band optical history of 37 blazars brighter than V-mag 17. This blazar variability monitoring started in 1991, with a fully robotic implementation operational from 1994. Despite of the limited budget, manpower and telescope size, such long-term program allowed to obtain light curves of blazars with a rather unprecedented continuity and sampling for about a dozen of our targets (considering data usually obtained by a single telescope). This effort was very useful to trigger observations and cam- paigns at other frequencies, to study the optical variability modes and the temporal behavior on intermediate and long timescales. Some highlights and examples of results are briefly reported.