The aim of this study is to study the effect of using planetariums as an outdoor learning environment regarding students' opinions. Therefore, descriptive qualitative research was used. The participants were from a school in Istanbul. Ten students, 4 male and 6 female, participated in a planetarium visit to a museum. The data of the study were obtained in 2016. A survey instrument consisting of 6 open ended questions and semi-structured interviews were used as data collecting tools. As a result of the collected data, using planetariums as outdoor activities in science education had a positive effect on students. The students found planetarium interesting and they stated that the visit was very fun.