  Variability Search Toolkit (VaST) is a software package designed to find
variable objects in a series of sky images. It can be run from a script or
interactively using its graphical interface. VaST relies on source list
matching as opposed to image subtraction. SExtractor is used to generate source
lists and perform aperture or PSF-fitting photometry (with PSFEx). Variability
indices that characterize scatter and smoothness of a lightcurve are computed
for all objects. Candidate variables are identified as objects having high
variability index values compared to other objects of similar brightness. The
two distinguishing features of VaST are its ability to perform accurate
aperture photometry of images obtained with non-linear detectors and handle
complex image distortions. The software has been successfully applied to images
obtained with telescopes ranging from 0.08 to 2.5m in diameter equipped with a
variety of detectors including CCD, CMOS, MIC and photographic plates. About
1800 variable stars have been discovered with VaST. It is used as a transient
detection engine in the New Milky Way (NMW) nova patrol. The code is written in
C and can be easily compiled on the majority of UNIX-like systems. VaST is free
software available at http://scan.sai.msu.ru/vast/
