Astronomy education research is a growing field but the attention given to informal educational activities, such as telescope observations, museum visits or planetarium sessions, is still relatively scarce. In consequence, the area is poorly studied and understood. Addressing this gap, this present paper examines informal educational practices in an astronomical observatory through detailed analysis of a complete turn at the telescope by a small child, who is observing the Sun with the assistance of a guide. Using Ethnomethodology and Conversation Analysis this study investigates how this activity was produced in terms of structure and methods, the skills the participants have, and how the interaction between the visitor and the guide occurs. The study of these naturally occurring activities is done in-depth by the repeated inspection of video data, in order to identify the characteristics of the interaction, the organization of the talk and its implications as an educational event. The interactional nature of linguistic exchanges is highlighted; and the study of these activities reveals the practical methods used by guides and public. The present study contributes to our understanding of telescope observations as informal education activities; and shows the importance of research methods that are sensitive to naturally occurring events.