A Star chart is a written document. It's used to represent the positions and movements of the stars, pretty much like a map. Astronomers usually use these for research or study. An O.W.L.-level wizard should be able of fill in a blank star chart based on some hours of sky gazing.
Behind the scenes
- For their Astronomy O.W.L. exam in their fifth year, each student has to "fill in a blank star chart" based on a few hours of observing the night sky.