1 Introduction

After years of search, the first optical counterparts to gamma-ray bursts (GRBs) have been found in 1997, beginning 3-20 hr after the onset of the high energy events. A power-law decline with the flux F $\propto t^\alpha$ is usually observed, where $\alpha$ is in the range -1.1 to -2.0. A review can be seen in Castro-Tirado (1999) and references therein. Under the assumption of the bursts being a repeating phenomenon, archival plates have been used in order to look for optical transient emission in the smallest GRB error boxes, and about 50 candidates have been identified so far, but most of them were rejected as they turned out to be plate defects (Hudec 1993).

Here we describe the Burst Observer and Optical Transient Exploring System (BOOTES), a set of instruments that is expected to contribute significantly to the understanding of GRBs and optical flashes.