ИСТИНА

Photographic plate archives contain a wealth of information about positions and brightness celestial objects had decades ago. Plate digitization is necessary to make this information accessible, but extracting it is a technical challenge. We develop algorithms used to extract photometry with accuracy ~0.1m in the magnitude range 13<B<17 from photographic images obtained in 1940-90s with the 40cm Sternberg institute's astrograph (30x30cm plate size, 10x10deg field of view) and digitized using a flatbed scanner. The extracted photographic lightcurves are used to identify thousands of new high-amplitude (>0.3m) variable stars. The algorithms are implemented in the free software VaST.