Prior research has demonstrated that neither children nor adults hold a scientific understanding of the big ideas of astronomy, as described in standards documents for science education [National Research Council [1996]. National science education standards. Washington, DC: National Academy Press; American Association for the Advancement of Science [1993]. Benchmarks for science literacy. New York: Oxford University Press]. This manuscript focuses on ideas in astronomy that are at the foundation of elementary students' understanding of the discipline: the apparent motion of the sun, moon, and stars as seen from an earth-based perspective. Lack of understanding of these concepts may hinder students' progress towards more advanced understanding in the domain.We have analyzed the logic of the domain and synthesized prior research assessing children's knowledge to develop a set of learning trajectories that describe how students' initial ideas about apparent celestial motion as they enter school can be built upon, through successively more sophisticated levels of understanding, to reach a level that aligns with the scientific view. Analysis of an instructional intervention with elementary students in the planetarium was used to test our initial construction of the learning trajectories. This manuscript presents a first look at the use of a learning progression framework in analyzing the structure of astronomy education.We discuss how this work may eventually lead towards the development and empirical testing of a full learning progression on the big idea: how children learn to describe and explain apparent patterns of celestial motion. (Contains 6 figures.)