This paper studies the attitudes of the traditional Chinese scholars towards technical natural knowledge and its experts, taking Chu Hsi and the calendrical astronomy as examples. On the whole, Chu Hsi accepted the expertise of the calendar experts. But at the same time he had a condescending and disdainful attitude towards them, because, in his view, their knowledge consisted merely of observations of obvious facts and practical computations for calendar-making and lacked attention to more fundamental cosmological problems. This attitude of Chu Hsi is best exemplified in his rejection of the calendar experts' 'rightward rotation theory' (右行說) in favor of his own and Chang Tsai's 'leftward rotation theory' (左旋說) for the movement of the sun, the moon and the planets. For he rejected the former theory without due consideration of the detailed reasons that the calendar experts actually needed it. This shows that Chu Hsi regarded their technical knowledge very lightly. It also testifies to Chu Hsi's strong concern with the actual structures and movements of the heaven and the luminaries, which, in turn, underlay his great interest in astronomical models and instruments. In conclusion, the scholars and the calender experts, while dealing with the same object, the heavens, were interested in different problems and thus used different approaches to them. The two groups were to a large degree isolated from each other. The above-mentioned attitude of scholars towards the calendar experts, then, is to be understood in this context. Similar conclusion can be reached concerning the other branches of technical knowledge like harmonics.