Dodaira Observatory (Hoshi to Midori no Sozo Center) in Japan — Full-Scale Stargazing at a Former National Observatory

Overview

Dodaira Observatory "Hoshi to Midori no Sozo Center" (Star and Green Creation Center) is a celestial observation and accommodation facility located at the summit of Dodaira Mountain (elevation 875.8m) in Tokigawa Town, Hiki County, Saitama Prefecture, Japan. It was previously used as an observation facility of Tokyo University's Tokyo Astronomical Observatory (now the National Astronomical Observatory of Japan) and retains a 91cm reflecting telescope that remains in active service today.

Its major attractions include excellent accessibility—approximately 2 hours by car from Tokyo—and comprehensive accommodation facilities suited for extended observing sessions.

Observation Environment

Dodaira Mountain's summit offers an open vista, particularly excellent to the south and west. At an elevation of 875m, positioned at the boundary between the Chichibu Mountains and the Kanto Plain, the northern sky displays the dark skies characteristic of the Chichibu region.

However, the southern and eastern aspects are affected by light pollution from the Kanto Plain, making it less dark than high altitude locations in Hokkaido or Nagano. Nevertheless, the night sky remains incomparably darker than urban centers, and on favorable nights the Milky Way is visible.

Facilities and Equipment

The primary feature is the 91cm reflecting telescope, available during celestial viewing events held twice monthly. These events are reservation-based and include commentary from astronomy professionals.

Accommodation options include Mongolian yurts, log houses, and bungalows, suitable for families and groups. Overnight guests can enjoy nighttime stargazing throughout their stay, allowing for sustained observing efforts.

Access

Approximately 50-60 minutes by car from either Higashi-Matsuyama IC or Arashiyama-Ogawa IC on the Kan-etsu Expressway. The mountain-top access road is paved but narrow in places, requiring attention to oncoming traffic. Public transportation is limited, so personal vehicle access is essential.

Observing Tips

Event schedules are available on the official website. Advance reservations are recommended due to high demand. Even without overnight accommodation, stargazing is possible from the parking area. Strong winds are frequent at the summit, so wind-resistant jackets are recommended.