Lake Okutama - A Nearby Stargazing Spot Where Tokyo's Darkest Night Sky is Encountered

Overview

Lake Okutama (Ogohara Reservoir) is Tokyo's largest artificial lake in Okutama Town, Nishi-Tama District. It's one of Tokyo city center's closest comprehensive stargazing spots, particularly recommended for celestial observation beginners.

Despite being within Tokyo, at approximately 530-meter elevation surrounded by mountains, the geography blocks city light pollution, allowing perception of the Milky Way's presence on favorable nights with the naked eye.

Observation Environment

Darkness around Lake Okutama vastly improves compared to central Tokyo, though retains light-pollution effects compared to dedicated astronomy sites. Bortle scale class 5 ratings allow bright magnitude 1-2 stars to shine clearly; winter's transparent nights reveal the Milky Way's subtle band.

Winter particularly enhances atmospheric transparency, providing optimal observation conditions. Lake surface reflected starlight creates a fantastical atmosphere.

Recommended Observation Points

The dam site observatory lies close to parking with southern sky open, ideal for planet and winter constellation observation. Nearby restrooms offer high convenience.

Near Mineyabashi Bridge deeper in the lake, even less light pollution allows darker skies—though nighttime has fewer visitors, safety suggests group visits.

Access

Public transportation accessibility from Okutama Station via approximately 15-20 minute bus journey is a major advantage. However, early final bus times make nighttime observation more practical by car. About 50 minutes from Hinode IC on the Kenodo Expressway; about 60 minutes from Hachioji IC on the Chuo Expressway.

Observation Tips

Binoculars greatly expand observation possibilities. Light pollution limits dark object visibility, but bright star clusters (Pleiades, Beehive Cluster) and binary stars remain binocular-viewable. Lakeside nights cool year-round—bring an extra layer.