The research reported here investigates the efficacy of a module in an Advanced Certificate in Education course in promoting conceptual understanding in Astronomy. The research attempted to find out how teachers' understanding of astronomy concepts and processes change after completing this module as well as the reasons for such changes, if any. The conceptual framework applied in the study is based on three constructs which influence learning. A pre- and post-module questionnaire, as well as interviews were the instruments used to collect data from a cohort of students registered for this module. The data revealed that very little conceptual change occurred. Possible reasons for the lack of conceptual change are: Classroom environments and instructional strategies that are not conducive to conceptual change; an emphasis on declarative knowledge with little attention paid to procedural knowledge and lastly, students own epistemological beliefs of what constitutes science knowledge and learning. (Contains 2 tables.)