  This paper describes a simple activity for plotting and characterizing the
light curve from an exoplanet transit event by way of differential photometry
analysis. Using free digital imaging software, participants analyse a series of
telescope images with the goal of calculating various exoplanet parameters,
including its size, orbital radius and habitability. The activity has been
designed for a high school or undergraduate university level and introduces
fundamental concepts in astrophysics and an understanding of the basis for
exoplanetary science, the transit method and digital photometry.
