日晷

The sundial is usually composed of copper and stone discs. The copper pointer is called the fin needle, which runs vertically through the center of the disk and acts as a neutral fin, so the fin needle is also called the watch. The stone disk is called the glazed surface, placed on the stone platform, the south high and north low, so that the glazed parallel to the celestial equator, so that the upper end of the glazed needle points to the north pole, the lower end points to the south pole.

The sundials, which are based on the direction of the sun's projection, are usually composed of pins (tables) and glazed surfaces (tables with scales). The use of sundials is a major human invention in the field of astrochronization, which has been used by humans for thousands of years.

A sundial device, also called a sundial, that uses shadows projected by the sun to determine the time. The sundial means the shadow of the sun. The modern day "dial" refers to a time-keeping instrument used by humans in ancient times to measure the time.

北京故宫里的日晷。故宫里保存着各种各样的日晷，用作计时。日晷是一种计时仪器，在春秋时期就已发明使用了，它是在一个特制的石板或木板面上，中间垂直立一细柱，把石面水平放置，面上再画刻度，成为了一个日晷，昼间看晷针投影到哪个刻度上就知道是什么时间，用日晷计时不能在夜间和阴天使用。　　日晷分为地平式日晷和赤道式日晷，在中国古代，由于隋代以前因为没有解决地平日晷晷面刻度与太阳周日视运动相对应的关系，不能正确完成它的测时功能，所以地平式日晷并没有真正运用。赤道式日晷是中国古代劳动人民的杰出创造，赤道式日晷的晷针垂直于晷面，且横穿晷心，晷盘平行于天赤道，正反面刻度相同，向北的一面用于春分至秋分这半年，向南的一面用于秋分至春分这半年。晷影在晷面上的方位角和时角相等，故晷影所指时刻为等分刻度形式。赤道式日晷设计制作比较简单，在不同地区安装，只要调节晷面的倾斜度与当地天赤道面重合就可以使用了，为了抵挡风的侵蚀，多为石质整圆晷面。郭守敬纪念馆第一展院就存放着一台赤道式日晷，以邢台地方真太阳时为依据，制定出相应的等分刻度，读出几时几刻，再根据时差曲线，换算成北京时间，与现在钟表上的时刻基本吻合，可见赤道式日晷现在不仅具有观赏性、还具有实用性。安放在故宫的日晷。日晷，本义是指太阳的影子。现代的“日晷”指的是人类古代利用日影测得时刻的一种计时仪器，又称“日规”。其原理就是利用太阳的投影方向来测定并划分时刻，通常由晷针和晷面组成。利用日晷计时的方法是人类在天文计时领域的重大发明，这项发明被人类沿用达几千年。故宫内的日晷就是故宫的计时工具。