This Astronomy activity (Is the Moon really larger when you see it on the horizon?) on the UniSchooLabs repository was originally developed at the Harvard-Smithsonian Center for Astrophysics In the MicroObservatory project. It includes an opening challenge (described below) that sets up the context for students.
Opening challenge
You’re sitting on a beach, watching the Moon rise. It looks big — really big. A few hours later, when it’s high in the sky, it looks a lot smaller. What’s going on? You know the Moon itself hasn’t shrunk. But is the image of the Moon on the horizon actually bigger? Or is your brain playing tricks on you? Your challenge is to design and carry out an experiment, using a remote telescope and its camera, to answer the question, 'Is the Moon really larger when it is near the horizon than when it is higher in the sky?
Educational Object Link