This paper attempts to explain the lack of dialogue between Indian and Chinese cosmologies in the astral sciences of the Six Dynasties and Tang. The history of cosmology in China, we are told, died in the eighth century, the final blow having been delivered by the monk Yixing. Almost everything we know about this history derives from three sources: Shen Yue and Li Chunfeng’s respective ‘heavenly patterns’ monographs (5th & 7th cent.) and Gautama Siddhārtha’s Kaiyuan zhanjing (729). The former, I argue, impart history with a neat telos that survives to our day: the history of cosmology is the history of instrumentation (two-dimensional diagrams and gnomon planes vs. three-dimensional sphere instruments); there were three true ‘schools’, but the contest was settled almost as soon as it began in the second century, the subsequent centuries being defined by irresponsible ideas that threatened the rightful winner. The success of Shen and Li’s frame, I argue, admitted no viable intellectual place for foreign ideas in their histories. Shifting perspective, I look at how Buddhists engaged with this discourse, examining the case of astronomers Gautama and Yixing, the dilettante Liang Wudi (r. 464-549), and the encyclopaedist Daoshi (7th cent)