National Astronomical Observatory of Japan

The Complete Image of Tairin-Suiyou-Kyugi

Historical illustration・

The Complete Image of Tairin-Suiyou-Kyugi

In the 19th volume of the “Kansei calendar (Note 1 and Note 2),” observational instruments were introduced. Two Suiyou-Kyugi (垂揺球儀 literally ‘pendulum type’) were described in this book. The first one is “Suiyou-Kyugi.” This was made by Asada Astronomical School, which Shigetomi Hazama belonged to. The second one is “Tairin-Suiyou-Kyugi” (大輪垂揺球儀 literally ‘large-wheel pendulum type’). Shigetomi Hazama’s son Jushin Hazama is said to have made that one. Both are pendulum chronographs. They are different from the ordinal clocks of those days; they are clocks for astronomical observations.

Suiyou-Kyugi is designed so that the first indicating plate counts 100 swings of the pendulum. Every full revolution of the first indicating plate moves the second indicating plate 1/10 of a revolution. Next, each full revolution of the second indicating plate moves the third indicating plate 1/10 of a revolution. Therefore, it can measure 10,000 swings of the pendulum. By adding another simple mechanism, it can measure up to 1 million swings. The pendulum swings about 60,000 times a day, so it is said that the precision of this instrument was within several seconds. Tairin-Suiyou-Kyugi (Note 3) is an improvement of this. It had two gears and the number of teeth on the first gearwheel was 600. Pendulum chronographs were introduced from the West, but the basic idea, displaying the number of pendulum swings on an instrument, was independently improved on by Shigetomi Hazama and others in Japan.

Translation by: Hiroko Tsuzuki and Ramsey Lundock (Public Relations Center, NAOJ)

(Note 1) “Kansei Rekisho” In 1798 (Kansei era 10), the Kansei calendar was enacted. The “Kansei calendar” summarizes how to calculate the movements of heavenly bodies and the instruments used for the observations to create the Kansei calendar. When revising the calendar, various observational instruments, other than Suiyou-Kyugi, were introduced and improved. Back

(Note 2) In addition to the standard Gregorian calendar, Japan uses a reign era calendar. The different eras are defined by changes in the Japanese government, and accompanied by changes in Japanese society. Back

(Note 3) The Suiyou-Kyugi and Tairin-Suiyou-Kyugi designs are shown at the following link.
Please click this link and open No.19, look from page 24 to page 28 for Suiyou-Kyugi, and from page 29 to page 34 for Tairin-Suiyou-Kyugi. (Japanese language only) Back

Image Data

Date Created1844 (Koka era 1)
AuthorsKagesuke Shibukawa, Yukitaka Yamaji, Nobuakira Adachi, Hidemochi Yoshida
CreditFrom the collection of the National Astronomical Observatory of Japan


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