Accurate photometry with digitized photographic plates of the Moscow collection

TL;DR

This paper presents algorithms for extracting high-precision photometry from digitized photographic plates, enabling the identification of new variable stars and making archival astronomical data more accessible.

Contribution

The authors develop and implement novel algorithms that achieve better than 0.1 magnitude accuracy from digitized plates, facilitating new astronomical discoveries.

Findings

Achieved photometric accuracy better than 0.1m for B magnitudes 13-17.

Identified thousands of new high-amplitude variable stars.

Provided free software VaST for photometry extraction from digitized plates.

Abstract

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 the accuracy of better than ~0.1m in the magnitude range 13<B<17 from photographic images obtained in 1948-1996 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 (>0.2m) variable stars. The algorithms are implemented in the free software VaST available at http://scan.sai.msu.ru/vast/