World Treasures – Planispheric Astrolabe (18th Century)

As they always say, “Forgery is ultimate flattery.” This is the Rolex of the 1700s, a craftsman at the top of his game with lots of forgery of his brand.

Parts Of A Planispheric Astrolabe by Abd al-A’imma

Copper alloy | Made in Iran, Isfahan, around 1700 |  H: 5.4 cm x W: 58.6 cm x D: 24.5 cm | Asian Civilisations Museum collection, Singapore

An astrolabe is a sophisticated inclinometer, historically used by astronomers, navigators, and astrologers. Its numerous functions include locating and forecasting the positions of the Sun, Moon, planets, and stars, determining local time based on latitude and vice versa, and surveying and triangulation.

It served all these purposes throughout classical antiquity, the Islamic Golden Age, the European Middle Ages, and the Renaissance. In the Islamic world, it was additionally employed to ascertain the Qibla direction and to calculate prayer times.

The ultimate state of the art of astrolabe was around 1720, just before the fall of the Persian Safavid dynasty, and it involved a craftsman named Abd al A’imma.² His skill as one of history’s finest astrolabe-makers is evident in his work held at museums around the world. Over 30 instruments and sundials are believed to have survived from the workshop of Abd al-A’imma. They are known for their accuracy and elegance. This specimen has been disassembled into its various components, arranged from front to back.

The pin holds all the various parts together. It is kept in place by sliding a wedge, called a “horse”, through the slot.

The rete (above) has been cut out to bear star pointers, shaped here like the tips of unfurling leaves, and the ecliptic ring. It can be rotated over the latitude plates underneath. The rete offers the instrument maker the greatest opportunity for artistic expression, and a great variety of designs exist.

Imagine the night sky with all the constellations. In combination with the rete, the plate (tympan) mirrors that sky at a given altitude. The North Pole is set at the centre of the plate, and altitudes are engraved as circles and arcs. An astrolabe usually comes with a variety of plates for different latitudes.

The mater is the main body of the astrolabe. The degree scale and hours of the day are marked along the rim, known as the limb. The throne (the decorative piece protruding from the mater) is used to suspend the astrolabe vertically to ensure more accurate readings.

Used as a sighting device, the alidade³ can be rotated to line up with a selected star or celestial body. The degree of the resultant altitude is read off the back of the mater, and used to determine the correct positions of the star pointers on the latitude plates.

Brass Astrolabe 黄铜星盘仪

Brass | Lahore, Emperor Humayun reign (r. 1530-1556) | Islamabad Museum collection (on tour in a special exhibition at National Museum of China)

An astrolabe crafted during the reign of the second Mughal Emperor, Humayun (1508–1556), is a significant early 16th-century artefact, often associated with the Lahori school of instrument-making. These brass instruments, characterised by their high scientific precision and artistic, finely engraved surfaces, reflect the emperor’s deep personal fascination with astronomy and astrology.

Gilt Bronze Planispheric Astrolabe 铜镀金简平星盘仪

Bronze | Qing dynasty, 20th year of Kangxi reign (1681) | D: 32.1 cm | The Palace Museum collection, Beijing. 铜｜清 康熙二十年（1681年）｜ 直径32.1厘米｜北京故宫博物院藏

In the Far East, another emperor was equally intrigue with astronomy. This Chinese Planispheric Astrolabe has a handle at the top, with the inscription “Jianping Yi” “简平仪” engraved on the upper part and star charts in Chinese engraved on the plates. The instrument consists of three sections: the upper section is the Northern Astronomical Instrument, with the twelve months engraved on the outer circumference (each month 30°), followed by the twelve two-hour periods (two-hour periods in total). The centre of the instrument is the North Pole, with a time dial above it.⁴

The inscription “Made in the midsummer of the year Xinyou in the 20th year of Kangxi’s reign”⁵ on the lower part, indicating that it was made by the Imperial Household Department of the Qing Dynasty in the 20th year of Kangxi’s reign (1681). This astrolabe is an important historical testament to Emperor Kangxi’s keenness in learning about astronomy and is of great value for our study of the ancient people’s understanding of celestial phenomena.⁶

Photos taken at Asian Civilisation Museum (Nov 2025), National Museum of China (Nov 2025), unless otherwise noted

Footnotes :

1. https://booklab.indiana.edu/lab-work/current-projects/astrolabe-2024-worksheet.html
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2. Astrolabes, iPhones and Fakery. 28 November 2017. https://blogs.mhs.ox.ac.uk/insidemhs/astrolabes-iphones-fakery/index.html
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3. The alidade was missing from the set in the museum when I visited and took the photos. However it was attached in a file photo from ACM’s Facebook page, reproduced here for completeness.
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4. 御制铜镀金简平仪，清康熙二十年（1681年），清宫造办处制作，星盘直径32.1厘米。清宫旧藏。
   　　简平仪分三重：上重盘为北地平盘，外周圈刻十二月份，每月30°，次内刻十二时辰，盘中心为北极，上附时刻盘。中重盘为天盘，其一面为北极恒星盘，上刻阴历日、赤道十二宫、周天360°、二十四节气、赤经线、黄道、银河系，沿赤道布列二十八宿，并按一至六等星标注。天盘的另一面为赤道南极恒星盘，除星象图有变化外，其余与北极恒星盘大致相同。下重盘为南地平盘，盘心象征着南极，中心设时刻盘、大游标，盘面刻有更线、节气线、日出没线等。简平仪顶端附提环，上端镌刻“简平仪”，下端镌刻“康熙二十年岁在辛酉仲夏制”铭文，为清宫内务府造办处所制造。
   　　因此简平仪未设置窥管，无法进行实测，但通过演示可求日出、日落时刻，日出、日入五更时刻，某时刻上中天的星，某时月在某方等。如求某时刻上中天的星（上中天的星即指某星通过子午圈的现象），即将北极恒星盘向左旋转，使当日太阳所在的赤道经度对准该时刻，视天盘午正位置上停留的星，即为所求该时刻上中天的星。
   https://www.dpm.org.cn/collection/clock/228943.html
   
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5. 康熙大帝与法国耶稣会士(图)
   http://www.sina.com.cn  2012年02月02日 17:45 三联生活周刊 微博
   
   “铜镀金简平仪”是在夜间窥星辰拟定星象或星位、视日影定时刻的仪器，属于星盘一类。这件直径大概32厘米的星盘简平仪共分三重，上重是北地平盘，中间一重是天盘，下重盘为南地平盘，上端镌刻“简平仪”，下端刻“康熙二十年岁在辛酉仲夏制”。北京故宫王慧向我解释说：“康熙时期宫廷制作了三件简平仪，这是其中的一件，在《皇朝礼器图式》卷三中有过记载。来华传教士和我国在制作这种形式的星盘中，都先后融入了中国传统天文学的内容，如根据不同需要加入十二辰、二十四节气和二十八宿等标识。” https://collection.sina.com.cn/zlxx/20120202/174554408.shtml
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6. Gilt Bronze Planispheric Astrolabe 铜镀金简平星盘仪
   Bronze | Qing dynasty, 20th year of Kangxi reign (1681) | The Palace Museum collection, Beijing.
   铜 | 清 康熙二十年（1681年） | 北京故宫博物院藏
   简平星盘仪顶端附提环，上端镌刻“简平仪”、下端镌刻“康熙二十年岁在辛酉仲夏制”铭文，可知为清宫内务府造办处于清康熙二十年（1681）制造。
   此件简平星盘仪是康熙皇帝学习天文知识的重要历史见证，也对我们研究古人认识天象历程具有极高的价值。
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