Xince zhongxing tubiao 新測中星圖表

Xince zhongxing tubiao 新測中星圖表 "Chart of newly measured determinative stars" is a book on astronomy written during the late Qing period 清 (1644-1911) by Zhang Zuonan 張作楠 (1772—1850), courtesy name Rangzhi 讓之, style Dancun 丹邨 or 丹村, from Jinhua 金華, Zhejiang. The book was finished in 1823 and is included in the series Cuiwei Shanfang shuxue 翠微山房數學. Other book of Zhang found in this series are Chuaiyue xiaolu 揣籥小錄, Hu sanjiao juyu 弧三角舉隅, Hujiao sheru 弧角設如, Jinhua guijing biao 金華晷景表, Baxian leibian 八線類編, Baxian duishu leibian 八線對數類編, Gaohu xicao 高弧細草, Liangcang tongfa 量倉通法, Fangtian tongfa buli 方田通法補例 and Cangtian tongfa 倉田通法.

The book is a revision of Hu Tan's 胡亶 (fl. 1649) Zhongxingpu 中星譜 from 1669 and Xu Chaojun's 徐朝俊 (c. 1800) Zhongxingbiao 中星表 (appendix of Xingyue ceshi 星月測時) from 1796. However, since these two sources were based on Johann Adam Schall von Bell's (Ch. Tang Ruowang 湯若望; 1591-1666) Hengxing chumo biao 恒星出没表, they contained significant errors.

For his corrections, Zhang Zuonan first used Jiang Lintai's 江臨泰 updated star measurements from 1744 and adjusted them for precession to project the star positions up to 1823. Based on these calculations, he created a celestial globe of measured star positions (jingchi xingqiu 徑尺星球). Using this globe as a reference, he then compiled the Xince hengxing tubiao 新測恒星圖表 "Charts of Newly measured fixed stars", Xince zhongxing tubiao 新測中星圖表 "Charts of newly measured determinative stars", and Xince genglou zhongxing biao 新測更漏中星表 "Table of determinative stars newly measured by the water-clock".

The Xince zhongxing tubiao takes the precise star positions at the winter solstice of as its reference. It provides tables listing the "central" or determinative stars (zhongxing 中星) of the star constellations for each of the 72 pentads (hou 候; five-day periods) throughout the year. The work includes 45 major star charts, along with supplementary tables, namely Chidao jingdu suicha biao 赤道經度歲差表 "Table of equatorial longitude precession", Zhongxing shike suicha biao 中星時刻歲差表 "Table of precessions of determinative stars", Taiyang huang-chi shengdu biao 太陽黄赤升度表 "Table of solar ecliptic and equatorial ascension", and Ershiba xiu huang-chi jidu biao 二十八宿黄赤積度表 "Table of the Twenty-Eight Lunar Mansions' ecliptic and equatorial degrees".

Zhang Zuonan expanded the number of pentads to 72, doubling that of previous similar tables. His data was precise to one arcsecond (jiaomiao 角秒) and one time second (shimiao 時秒). Using the tables, one could systematically adjust the values year by year and day by day to determine the required determinative star timings. This system allowed both for determining time based on a determinative star and for verifying its position based on time.

However, Zhang's charts were not based on his own astronomical observations. Since there was an 80-year gap from 1744 to 1823, relying solely on extrapolation could not perfectly match actual celestial conditions, inevitably affecting accuracy. Nevertheless, in terms of technical skill in table-making, Zhang surpassed his predecessors and provided valuable experience for future scholars producing similar charts.

Zhang's Xince genglou zhongxing biao was synchronised with the Zhongxinggeng lu 中星更錄 "Updated records of determinative stars" issued by the Directorate of Astronomy (qintianjian 欽天監). This supplementary work primarily focused on determinative star timings according to water clocks (genglou shike 更漏時刻).

Using star charts to determine time was ultimately inconvenient, especially since most people did not recognise celestial bodies—rendering such charts useless to the general public. Therefore, in 1851, Feng Guifen 馮桂芬 (1809-1874) and others compiled the Xianfeng yuannian zhongxing biao 咸豐元年中星表 "Determinative stars table of 1851", increasing the number of observed stars to 100, the introduction and gradual development of the clock and watch industry in China naturally led to the obsolescence of such star-based timekeeping tables. As a result, the star chart compiled by Feng and his colleagues became the final work of its kind.