The “Transit Instrument Building” stands in the flower petals fluttering down among the sunshine filtering through the trees. The “Repsold Transit Instrument” displayed inside played an active role as an observational research instrument up through the mid-20th century.

The capital pattern projecting from the top part of the exterior wall and the fixtures of the entrance eaves are decorated with the straight line patterns of the Vienna Secession style which was popular at the time of construction in 1925, giving the building a simple yet graceful facade.

This building has a roof which can open and close. If you slide the roof open and open the casement windows, it is possible to see the sky to the north, up through the zenith, to due south. It hides an unexpected boldness you wouldn’t expect from the quiet atmosphere.

The soft colors of spring envelop NAOJ Mitaka Campus. In the public areas, you can enjoy the blossoms marking the changing of the seasons.

Overview of the Repsold Transit Instrument

Displayed in the center of the Transit Instrument Building is a transit instrument manufactured in Germany in 1880 (13th year of the Meiji Era). Until the Observatory moved to Mitaka, this instrument was in Iikura, Azabu where it was used to determine longitude and time. The time signal cannon was fired at noon based on the time determined from Repsold Transit Instrument observations. In Mitaka, this instrument was used for observations to determine the right ascension of Solar System bodies and fixed stars; it completed this role in 1962.

As an important observational instrument which supported the dawn of modern Japanese Astronomy, the Repsold Transit Instrument was designated as an important cultural property of Japan in 2011.

Text by: Seiichiro Naito (Public Relations Center)
Translation by: Ramsey Lundock (NAOJ)

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• Transit Instrument Building