The Optical Variability of PKS 1510-089, PKS 1622-297 and AP Librae

The results of a five-year photometric monitoring program for the three southern hemisphere blazars, PKS 1510-089, PKS 1622-297 and AP Librae will be presented. Rapid, large amplitude variations are present on timescales ranging from less than a day to years. These variations will provide constraints on the emission mechanisms and the size of the emitting region. The implications of these results will be discussed.