National Astronomical Observatory of Japan

Solar Tower Telescope

Einstein Tower

Regarding the preventive actions of the novel coronavirus (February 21, 2020)

The regular events at NAOJ Mitaka Campus, such as public visits, Stargazing Parties and the 4D2U Dome Theater, may be canceled because of the ongoing coronavirus concerns. For the latest information regarding these events, see our website or SNS. For those who plan to visit Mitaka Campus, please note the following points:
・If you have, or think you may have, had close contact with someone infected with COVID-19, please refrain from visiting Mitaka Campus.
・In case you have cold-like symptoms, please refrain from visiting Mitaka Campus.
・Take appropriate preventive actions, such as washing your hands with soap and wearing a mask, to protect yourself from the infection.

Solar Tower Telescope (Einstein Tower)

Only the exterior is viewed.

The Solar Tower Telescope was designed by Facility Department of Tokyo Imperial University and constructed by Nakamura Komusho in 1930. The construction is reinforced concrete with five floors above ground and one basement floor (only this part was built in 1926). The solar light entering through the top dome that the height is about 20 m is brought in and reflected at a perpendicular angle with a 60 cm diameter coelostat (two flat mirrors). And then the light is divided into a seven-colored spectrum at the semi-underground large dark room in north. It is called as "Tower Telescope" because the tower itself functions as a telescope tube.

While the structure mostly consists of straight lines, the eaves and balconies have curves, and the exterior walls are embellished with brown scratch tiles skillfully combining difference colored of uneven burning.

Because the structure of building has the same research purpose as the Potsdam Astrophysical Observatory (Einstein Tower) in the suburbs of Berlin City, it is also called as "Einstein Tower".

This building has been registered a tangible cultural property of Japan in July, 1998.


Aperture60 cm
Cassegrain type reflector telescope
Aperture48 cm
Focal length22 m
Target of observationsolar spectroscopic observation
SizeDiameter 5 m, Height about 20 m
RemarksRegistered Tangible Cultural Property (Structures)
Brief history
(Taisho era 15)
Completion of semi-basement building of spectrometer room
(Showa era 5)
Completion the tower part of building
(Showa era 32)
Changed to current optical system
(Showa era 43)
Research observation end
July, 1998
(Heisei era 10)
Registered as Tangible Cultural Property of Japan
(Heisei era 12)
Open to the public only exterior appearance
(Heisei era 22)
Become able to visit inside with guided