Japan 1949 – Mizusawa Latitude
Observatory
The International Latitude Observatory at
Mizusawa in northern Japan was founded in 1899 as one of six
stations of the International Latitude Service (ILS, the
forerunner of the modern International Earth Rotation Service),
with Hisashi Kimura as
its first director. The other ILS observing stations were:
Tschardjui (Russia), Carloforte (Italy), Gaithersburg (USA),
Cincinnati (USA) and Ukiah (USA), all chosen to be close to the
same latitude, 39° 08’ north. By measuring precise
star positions, these observatories tracked slight changes in
latitude caused by motion of the Earth’s axis of rotation
(polar motion).
Mizusawa, Carloforte, Gaithersburg and
Ukiah were initiallly equipped with a 108-mm (4.25-inch) Visual
Zenith Telescope made in Germany. However, the telescope shown
on this stamp commemorating Mizusawa’s 50th anniversary
is the 178-mm (7-inch) Floating Zenith Telescope, a
photographic instrument introduced at Mizusawa in 1939, made in
Japan but with Zeiss optics.
Mizusawa Latitude Observatory served as the
Central Bureau of the ILS from 1922 to 1934 and again from 1962
to 1987 (when the ILS became the International Polar Motion
Service). It is now known as Mizusawa Astrogeodynamics
Observatory.
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