Twenty-nine Zulu-speaking primary school teachers were enrolled for a certificate in-service science education course. Initially, informal classroom discussions with these teachers pointed out poor conceptual knowledge in basic astronomy. This study investigated teachers' scientific and indigenous conceptions of the Earth-Moon-Sun (E-M-S) system, namely, the motion of Earth relative to the Sun, the day/night cycle, Moon phases and seasons. It examined teachers' astronomical experiences from a socio-cultural constructivist perspective through individual and focus group interviews. The phenomenographic approach was used to analyse the data. The findings of the study are in conformity with the global literature in science education where primary school teachers hold a number of incorrect conceptions of the E-M-S system. In addition, teachers also hold indigenous conceptions of the E-M-S system related to African traditional and agricultural practices.