In recent years, short question-and-answer activities known as lecture tutorials that are designed to help students work with and discover concepts for themselves, rather than simply being told about them (lectured to) have become a popular tool for learner-centred teaching of introductory college astronomy. Students on such a course are usually non-science majors fulfilling a general education requirement and have a limited background in mathematics. The following is a description of the development, use and assessment of a lecture tutorial. (Contains 2 figures, 1 footnote, and 3 tables.)