National Astronomical Observatory of Japan

Gautier Meridian Circle Building

Gautier Meridian Circle Building

Meridian Circle is the innovation telescope that can observe position (right ascension and declination) of objects on meridian precisely. For that, it has the mechanism that is rotated only exactly in direction of the meridian plane (North-South direction).

The Gautier Meridian Circle was made in France in 1903, and it was bought at the price 20,000 yen at that time in 1904. It was moved to the Mitaka campus in 1924 and served as one of the major astronomical instruments of the Tokyo Astronomical Observatory. Also, when the Great Kanto Earthquake in 1923, it was escaped from the damage of the earthquake because it had been packed for relocation.

It had been served for recording the positions of stars, the Moon, and planets for a long time, but a new photoelectric meridian circle once replaced Gautier Meridian Circle in 1982. However, equipped with a newly developed CCD micrometer, the Gautier Meridian Circle served again from 1992 for about ten years for measure the positions of faint objects such as QSOs.

The building of observation room was built in 1924. By combining unusual shapes that are semi-circle dome and trapezoid entrance roof, it aim for beautiful design.


Gautier Meridian Circle
Aperture20 cm
Focal length310 cm
Target of observationaccurate positional observation of celestial object
Brief history
(Taisho era 13)
(Showa era 58)
Visible observation end
(Heisei era 4)
Installation of CCD micrometer
Around 2000Research observation end
April, 2014
(Heisei era 26)
Registered as tangible cultural property of Japan