In this design study, the authors documented means by which preservice teachers experienced mathematics and science associated with understanding the Moon and sky as they participated in project work within their mathematics and science methods course. The authors examined the way preservice teachers applied mathematics needed to accomplish project tasks in an astronomical context and compared project work of 6 groups. The groups experienced difficulties applying basic mathematics such as scaling, ratios, and sine curves, requiring just-in-time scaffolding lessons to facilitate project progress. In their analysis of participants' pre- and post-scientific and mathematical understandings needed to grasp lunar concepts, authors found that preservice teachers made significant gains in both areas. (Contains 7 figures and 4 tables.)