Astrophysics with Astronomical Plate Archives

The digitised astronomical plate archives represent a source of unique data for various scientific projects including analyses of objects such as AGN, blazars, cataclysmic variables, galactic X-ray sources, various transients, and other objects. These data may easily provide very long term monitoring over very extended time intervals (up to more than 100 years) with limiting magnitudes between 12 and 23. The archival astronomical plates represent a unique database for various scientific projects, and, after digitization, can be easily implemented into the Virtual Observatories. They can provide thousands of exposures for any celestial position, reaching monitoring intervals of up to few years of continuous monitoring i.e. tens of thousands of hours. There are nearly 3 millions astronomical archival plates located at different observatories [1]. The recent efforts to digitise the plates and the corresponding software development significantly facilitate the extraction of unique scientific data from archival records and related reductions and analyses. The photographic sky monitoring is available for more than 100 years. However, only the recent development of photographic scanners and powerful computers allows an efficient extraction of scientific data. Some of the archives have very high quality plates achieving limiting magnitudes of up to 20–23 (direct imaging) and /or 17– 19 (spectral with objective prism). Recent efforts focus on digitisation and automated evaluation. Some of the archives already have devices for digitisation of plates and few of them have already started extended digitisation of the plates (e.g. Sonneberg Observatory about 60 000 plates already scanned). Some of the archives have started projects to develop high quality scanners to convert all plates into files/CD ROMs (e.g. The Royal Observatory Brussels). There are efforts to use these data for automated evaluation of objects on the plates and creating their light curves. There are attempts to create an European Plate Centre in Brussels, Belgium (the UDAPAC project, for more details see http://midasf.oma.be/fido/project.html) all interested people can contact us at rhudec@asu.cas.cz. Most of the sky patrol programs are already closed. However, two of the photographic sky patrols are still in operation, regularly taking photographic patrol images every clear night. The Ondrejov all sky patrol operated for monitoring of bright meteors has a sensitivity of 12 in the best case and a very large sky coverage (full visible sky hemisphere). The Sonneberg sky patrol is operated for variable stars simultaneously in two colours with limits 14–15 but with a less