Zhongxingpu 中星譜

Zhongxingpu 中星譜 is a book on stars written during the early Qing period by Hu Tan 胡亶, courtesy name Baoshu 保叔, style Lizhai 勵齋, from Renhe仁和 (today part of Hangzhou 杭州, Zhejiang). He obtained the jinshi degree in 1649 and was a Hanlin bachelor (Hanlinyuan shujishi 翰林院庶吉士) released as a junior compiler (sanguan shou bianxiu 散館授編修), and later circuit intendant of Su-Chang-Zhen 蘇常鎮. He also wrote Zhoutian xianjie tu 周天現界圖. Of his writings, the surviving works are collected in the Lizhai wenji 勵齋文集.

The book of 1 juan length was finished in 1669. It records the stars visible throughout the entire night, from sunset to sunrise, in sequential order. This approach is more detailed than the ancient method, which only recorded stars visible at dusk and dawn. The book is divided into twenty-four sections. The timing of dusk and dawn is based on the Chongzhen Calendar 崇禎曆書 (later known as the Shixian Calendar 時憲新法 or New Calendar 新法曆書), which defines dusk and dawn as the moments when the sun is 18 degrees below the horizon. The full-day time system follows divides the day into 24 hours and 96 quarters of an hour (ke 刻). In ancient methods, only the central stars (zhongxing 中星) within the 28 lunar mansions (ershiba xiu 二十八宿) were recorded. However, this book expands the selection by adding 17 more stars outside the traditional mansions, making a total of 45 principal stars. These 45 stars are all located near the ecliptic and celestial equator (huang-chidao 黄赤道), with each constellation containing a varying number of stars, but only one representative star (nian ge zuo yi xing 拈各座一星) from each is recorded in the catalog.

The recorded culmination times of these stars correspond to the first day of each solar term (jieqi 節氣). For subsequent days, the culmination time can be calculated by subtracting four-fifths of a ke (i.e., 12 minutes) per day. The specified time standards follow those set by the Shixian Calendar, which was derived from the Chongzhen Calendar and officially promulgated in the capital (Shuntian prefecture 順天府). Since the dusk and dawn times of each solar term do not always coincide with the culmination of these stars, the book also provides the longitudinal and latitudinal coordinates of major stars relative to the lunar mansions. This addition allows for comparisons with the ancient system to verify their consistency or differences.

The Zhongxingpu is considered a companion work to the Zhongxingbiao 中星表 "Catalogue of stars" and Zhongxing genglu 中星更錄 "Record of star culminations", compiled in 1744 as part of the compendium Yixiang kaocheng 儀象考成. However, the star positions in Zhongxingpu were not derived from direct observation but were calculated based on the Chongzhen Calendar and the Yixiang kaocheng. Consequently, the positions deviated from actual measurements and did not account for precession, leading to increasing errors over time, which limited its longevity and accuracy. Hu's Zhongyingpu is considered one of the more refined star charts for timekeeping from the early Qing period.

The book is included in the imperial series Siku quanshu 四庫全書.