Students learn how using spectrographs helps people understand the composition of light sources. Using simple materials including holographic diffraction gratings, students create and customize their own spectrographs—just like engineers. They gather data about different light sources, make comparisons between sources and theorize about their compositions. Before building spectrographs, students learn and apply several methods to identify and interpret patterns, specifically different ways of displaying visual spectra. They also use spectral data from the Cassini mission to Saturn and its moon, Titan, to determine the chemical composition of the planet's rings and its moon's atmosphere.