Chinese Needham Type-B Diptych, c.1880-1910

Wooden Diptych Sundial, Needham Type-B. Chinese-made, late 18th-early 20th century. Including compass & folding brass gnomon. For use at latitude 35°N. Inclination adjustable by hinged strut - 12 notches corresponding to 12 solar periods of the year. Table engraved on dial. Intended to be used facing north, & has a compass that allows the user to check their orientation, ensuring the position of the sun is accurately aligned for correct time to be read.

This sundial is based on the Chinese solar calendar, Jiegi, and lists the 24 solar terms of the year from, Duxue meaning Great Snow, to Xiazhi (i.e. summer solstice). Intended to be adjusted throughout the year to account for our celestial position (seasons), by altering the base angle of sundial rest.

Based on the position of the sun, Chinese timekeeping divided days into 12 equal units, or double hours, known as Shi, which range from Tzu to Hai. Each double hour was named after one of the 12 earthly branches, associated with Chinese zodiac. There are further divisions within this time standard such as Ke and Fen (exact calculations of these units have varied throughout dynasties). And though China now utilizes the Coordinated Universal Time (UTC) standard time division, the characters used for the previous time standard are now applied to these divisions.

Featured in the Adler Planetarium. 

Featured in the Science Museum Group.

Dimensions: 5.5 cm. x 11.5 cm. x 1.5 cm.

Diameter (Inner Compass): 2.5 cm.

Weight: 1.4 oz.