Education is increasingly being framed by a competence mindset; the value of knowledge lies much more in competence performativity and innovation than in simply knowing. Reaching such competency in areas such as astronomy and physics has long been known to be challenging. The movement from everyday conceptions of the world around us to a disciplinary interpretation is fraught with pitfalls and problems. Thus, what underpins the characteristics of the disciplinary trajectory to competence becomes an important educational consideration. In this article we report on a study involving what students and lecturers discern from the same disciplinary semiotic resource. We use this to propose an Anatomy of Disciplinary Discernment (ADD), a hierarchy of what is focused on and how it is interpreted in an appropriate, disciplinary manner, as an overarching fundamental aspect of disciplinary learning. Students and lecturers in astronomy and physics were asked to describe what they could discern from a video simulation of travel through our Galaxy and beyond. In all, 137 people from nine countries participated. The descriptions were analysed using a hermeneutic interpretive study approach. The analysis resulted in the formulation of five qualitatively different categories of discernment; the ADD, reflecting a view of participants’ competence levels. The ADD reveals four increasing levels of disciplinary discernment: Identification, Explanation, Appreciation, and Evaluation. This facilitates the identification of a clear relationship between educational level and the level of disciplinary discernment. The analytical outcomes of the study suggest how teachers of science, after using the ADD to assess the students disciplinary knowledge, may attain new insights into how to create more effective learning environments by explicitly crafting their teaching to support the crossing of boundaries in the ADD model.