《汉书·志·天文志》
北斗的第一星临近参宿之首。在黄昏观测北斗星斗柄的指向来判定时令，斗柄，主预示华夏以西南地区。
用昏建者杓；杓，自华以西南。
The first star of the Big Dipper is near the head of the Canis constellation. Observe the direction of the handle of the Big Dipper at dusk to determine the season, the handle of the Big Dipper, mainly indicates the southwest region of China.