St. John’s College maintains both an observatory and a planetarium on the Annapolis campus. College community members use the planetarium in conjunction with the laboratory and mathematics tutorials. In addition, students are encouraged to work on special projects using the telescopes. Regular, informal stargazing sessions are held after seminars on Monday and Thursday evenings.

Both facilities are also open to the public as astronomical events and activities of general interest arise. The planetarium is named for Theodore R. McKeldin, a former governor of Maryland.