The nature of expertise in astronomy was investigated across a broad spectrum of ages and experience in China and New Zealand. Five hypotheses (capable of quantification and statistical analysis) were used to probe types of expertise identified by previous researchers: (a) domain-specific knowledge-skill in the use of scientific vocabulary and language and recognising relationships between concepts in linguistic and schematic forms; (b) higher-order theory in terms of conceptual structure and enriched scientific knowledge and reasoning; with an expectation of cultural similarity. There were 993 participants in all, age 3-80 years, including 68 junior school pupils; 68 pre-school pupils; 112 middle-school students; 109 high-school students; 79 physics undergraduates; 60 parents; 136 pre-service primary teachers; 131 pre-service secondary teachers; 72 primary teachers; 78 secondary teachers; 50 amateur astronomers and astronomy educators; and 30 astronomers and physicists; with approximately equal numbers of each group in both cultures; and of boys and girls in the case of children. For them, the methodology utilised Piagetian interviews with three media (verbal language, drawing, play-dough modelling), and for adults a questionnaire inviting responses in writing and drawing was used. The data from each group were categorised into ordinal scales and then analysed by means of Kolmogorov-Smirnov two-sample tests. The findings supported the hypotheses with evidence of all forms of expertise increasing with experience in both cultures ([alpha] level 0.05). The relative gains, overlaps and deficits in expertise across the novice-expert continuum are explored in detail. (Contains 1 table and 8 figures.)