“辰星正四时”暨辰星四仲躔宿分野考

A Study of Mercury as the Season-Telling Star and the Fenye System Based on Mercury's Movement

《天官书》中称辰星有正四时的功能,并记载了辰星四仲躔宿命国的分野模式。汉晋时人基于经验认为辰星通常只在四仲出现,从而认为辰星可以"正四时"。这一观念不符合天文科学层面之事实,但具有占星学上的意义——时人将辰星在四仲以外的时间出现视作灾异。辰星四仲躔宿命国的分野模式,包含了时间(四时)、星宿、空间(国)三要素。时间(四时)与国的对应受到五行观念的影响。分野模式中以齐、楚、汉、中国作为四方之国,则是受到了汉初政治地理格局的影响。而这一判断有助于推测《开元占经》所引《石氏星经》中相关内容的形成时代。

Tianguan Shu, one chapter in Shih Chi, states that observing Mercury could deter- mine the seasons. It also depicts the Fenye system that Mercury＇s seasonally lodging constellations re- spectively correspond to four terrestrial states. This article points out that during Han to Jin period Mercury was generally thought to be observed in the four mid-season months, hence the conviction that it tells seasons. Such a view, though not conforming to modern astronomy, was astrologically sig- nificant, so that irregular activities of Mercury beyond mid-seasons were deemed inauspicious. The Mercury-Based Fenye system consists of three elements time, constellations and states, with a correspondence between the latter two as shaped by the notion of Five Phases. And it is an effect of the geopolitical landscape in early Han that Qi, Chu, Elan and Zhongguo were positioned as the four states in four geographical directions in the Fenye system above. This last point, incidentally, is useful for dating the almost identical record in Shi Shi Xingjing（Shi＇s Catalogue） quoted by Kaiyuan Zhanfing.