Mizusawa (水沢市, Mizusawa-shi) was a city located in Iwate Prefecture, Japan. It is currently part of the city of Ōshū. Mizusawa is home to one of the six International Latitude Observatories. The observatories were close to the parallel of 39 degrees 8 minutes north latitude. They worked together to study the Earth's "wobble" using stars selected by Dr. Kimura, the astronomer in charge of the Mizusawa station. Twelve groups of stars that had six pairs of stars each were chosen.