Stargazing in Iruma, Saitama, Japan

Dark-sky rating for Iruma

Iruma, Saitama, Japan is a small city (population about 147,166). A place this size typically has a rural to suburban transition: the Milky Way core can be glimpsed on clear, moonless nights. That is an estimate of Bortle class 4–5 from population, not a measurement: the real value depends on the exact spot you observe from.

For a measured reading at any point, open the live Dark Sky map.

Nearest dark-sky places and observatories

• Nobeyama Radio Observatory · observatory · about 82 km away

Milky Way season in Iruma

The bright core of the Milky Way stays low, so you need a clear southern or northern horizon. It climbs at least 20° above the horizon during astronomical darkness in March, April, May, June, July, August, September, peaking in June at about 25°.

• The north celestial pole stands 35.8° above the horizon, so stars within 36° of it never set from here.
• About 79.3% of the whole sky rises above the horizon at some point in the year from this latitude.
• The Milky Way's core in Sagittarius culminates about 25.2° up, staying low, so a clear southern horizon matters.
• At 126 m elevation, roughly 1% of the atmosphere's mass is already below you, which measurably reduces extinction near the horizon.

Tonight and aurora

As of October 16, 2026 (UTC) the Moon is a Waxing Crescent at 28% illumination. Aurora at 35.8° latitude generally needs about Kp 9.0.

Nearby places

• Kawagoe, Saitama, Japan
• Fuchu, Tokyo, Japan
• Aihara, Kanagawa, Japan
• Saitama, Saitama, Japan
• Tokyo, Tokyo, Japan
• Machida, Tokyo, Japan