Astronomy textbooks images: do they really help students?

In this paper we present a study on the difficulties of secondary school students in interpreting textbook images of elementary astronomical phenomena, namely, the change of seasons, Sun and lunar eclipses, Moon phases. Six images from a commonly used textbook in Italian secondary schools were selected. 45 minutes interviews about the astronomical concepts related to the images were carried out with eighteen students attending the last year of secondary school (age 17-18). Students' responses were analyzed through a semiotic framework based on the different types of structures of visual representations. We found that the wide range of difficulties, which students show, arises from naïve or alternative ideas due to incorrect or inadequate geometric models of the addressed phenomena. As a primary implication of this study, we suggest that teachers should pay attention to specific iconic features of the discussed images as, e.g., the compositional structure, and the presence of real/symbolic elements.