Solar Tower Telescope (National Cultural Monument)
The Solar Tower Telescope was purchased from Zeiss, Germany, in 1928. The building decorated with brown brick which is the same as the Main Library of Tokyo University, was erected in 1930. The structure is similar to the Einstein Tower of Potsdam Observatory, so that this tower has also been called the Einstein Tower.
In the dome at the top of the 18.2 m high tower is installed a coelostat system (two flat mirrors with 45 cm diameter). The primary optics was originally a 45 cm lens, and in 1957 it was changed to a Cassegrain mirror system. At the basement is arranged a spectrograph with 12 m focal length, and high dispersion solar spectra can be obtained. The flare spectra of hydrogen Balmer lines and the implication of filamentary structure of flare regions by Suemoto and Hiei, and the magnetic field structure of sunspots by Nishi and Makita were the main scientific results obtained with this instrument. The basic experiments of polarimetry initiated here have led to the completion of the Vector Magnetograph at Okayama Observatory.
The Tower is no longer used for research recently, but its historical value and unique architecture is recognized and is designated as National Cultural Monument in 1998 February.
Other historical buildings in the Mitaka campus include the Dome of 20cm Zeiss Refractor (also designated as National Cultural Monument in 2002 March), built in 1921. The Helioscope Building, built in 1920, where H-alpha flares were observed with the Spectro-Helioscope and Calcium K-line images were observed with theSpectro-Heliograph, was closed in 1999 spring.
