ASTRONOMICAL PLATE ARCHIVES AND SUPERMASSIVE BLACK HOLE BINARIES

The recent extensive digitisation of astronomical photographic plate archives, the development of new dedicated software and the use of powerful computers have for the first time enabled effective data mining in extensive plate databases, with wide applications in various fields of recent astrophysics. As an example, analyses of supermassive binary black holes (binary blazars) require very long time intervals (50 years and more), which cannot be provided by other data sources. Examples of data obtained from data mining in plate archives are presented and briefly discussed