CAS-Observatory is the amateur astronomy program associated with the Astronomy Club of Friedrich-Schiller-Gymnasium in Preetz. The club welcomes interested students from Year 8 onward and provides opportunities to learn practical astronomy through observation, research and image-making. Its activities cover astrophotography, including photographing galaxies, stars, planets and asteroids, as well as spectroscopy, photometry and astrometry. Participants can explore how to study the temperatures and composition of stars, investigate supernovae and exoplanets, observe minor planets, and determine stellar positions or planetary orbits.

The website also presents astronomy images and observations, including the Crab Nebula, the Ring Nebula in Lyra and asteroid Katanga. Alongside the school club, CAS-Observatory connects with a private observatory and offers SAM, the Simple Astroprojekt Manager, a software tool for organizing astronomy images collected by the group and private observers. An astronomy wiki and information about the observatory, software and club activities further support learning and sharing. Overall, CAS-Observatory combines student education, amateur research, observational resources and astronomy-related software.