We investigated to what extent secondary school students have insight in the apparent motion of the Sun and stars (AMoSS). We used the AMoSS test instrument, which focuses on distinctions between different aspects of the apparent motion of the Sun and stars. It consists of 12 multiple-choice questions accompanied by explanations. We administered the test to students of the fifth year (16–17 years old) of six Belgian secondary schools (N = 410) during a science lesson in school and asked them to explain their choices. We found that, despite instruction, most students only demonstrate a rudimentary understanding of the apparent motion of the Sun and stars for different times during the day, different times during the year, and different locations of the observer. Moreover, we see a clear distinction between the responses to the questions about the Sun and stars. Thanks to the classification system that we developed to categorize the written explanations and a latent class analysis, we are able to identify different mental models that students use to answer questions about the apparent motion of the Sun and stars.