After dark

Japan's Night Sky

One of the most light-polluted countries in the world also has three certified dark sky places and a southern latitude most of Europe does not reach. Where the stars actually are, and the four things that decide whether you see them.

The Milky Way rising over a dark bay with a scatter of distant town lights on the far shore — Japan · August 2022

Japan is a bad country for stargazing and a very good one, depending on where you stand. The main island corridor from Tokyo to Osaka is among the most light-polluted ground on earth. Go two hours off it, or fly south, and the sky is as good as anywhere in temperate Asia.

Four things decide what you see, and only one of them is luck.

At a glance

Milky Way core: Visible from roughly March to October. June to August it is up in the evening
Moon: Plan for the three nights either side of new moon. A half moon ends it
Best latitude: Okinawa and the Yaeyama islands, at 24°N, reach stars Honshu never sees
Certified dark: Iriomote-Ishigaki National Park (2018), Kozushima (2020), Bisei in Okayama (2021)
Season for clarity: Winter air is clearest; summer has the galaxy but also haze and typhoons

The moon matters more than the place

A dense field of stars with the band of the Milky Way crossing the frame — Nothing in the frame but sky. This needs a dark site and a dark moon, in that order of difficulty.Japan · September 2023

A full moon at a perfect dark site gives you a worse sky than a new moon at a mediocre one. The moon is the brightest source of light pollution in the country on about ten nights a month, and it is the only one that is entirely predictable years ahead.

Check the lunar calendar before you book anything. The three nights either side of new moon are the window; after that the moon rises earlier each evening and takes the galaxy with it.

The second question is what time the Milky Way core is up. In June it clears the horizon in the late evening and is overhead after midnight. By October it is already setting when the sky goes dark, which is why the same site gives a completely different result in two different months.

What light pollution actually looks like

A faint starfield above a dark ridge, with a strong orange glow spreading along the horizon — A reasonable sky overhead and a city forty kilometres away. The glow is what you are travelling to escape.Japan · June 2021

This is the condition most people find when they drive an hour out of a Japanese city at night. Overhead is acceptable; the bottom thirty degrees of the sky is gone, replaced by an orange dome from a town over the ridge.

It matters because almost everything worth photographing — the galactic core, a rising constellation, a mountain against the sky — sits in exactly that lower band. Height and distance both help, but direction helps most: put the glow behind you and shoot away from it.

The Milky Way standing over a dark coast, with a line of lights running along a causeway below — A coast facing away from the mainland. Everything bright in the frame is below the horizon line.Japan · September 2023

Coasts and lakes work for this reason. Half the horizon is water, which emits nothing, and the land behind you blocks the rest.

Where the dark is

Japan has three sites certified by DarkSky International, and the certification is a reliable signal because it requires the local authority to control its own lighting, not merely to be remote.

Iriomote-Ishigaki National Park, in the Yaeyama islands, was the first, in 2018. It is also the single best reason to go: at 24°N the islands see 84 of the 88 constellations, including the Southern Cross low in the south in spring, which is not visible from the Japanese mainland at all.

Kozushima, a volcanic island 180 km south of Tokyo and administratively part of it, was certified in 2020. It is reachable overnight by ferry from Takeshiba in central Tokyo, which makes it the most practical dark sky on this list for anyone based in the capital.

Bisei, in Okayama prefecture, was certified in 2021 — the first Dark Sky Community in Asia. It is a mainland town that has regulated its street lighting since the 1980s, and it has a public observatory.

The Milky Way rising vertically above a small lit islet seen across rock and shallow water — Okinawa in July: the core stands almost vertical, and the cloud comes and goes all night.Okinawa · July 2022

Beyond the certified three, the practical rule is elevation and distance. The high plateaus of Nagano and Gunma, the Noto and Shimokita peninsulas, the interior of Hokkaido and any of the smaller inhabited islands all give a genuinely dark sky on a clear new-moon night.

Practical

Go in winter if you want stars rather than the galaxy. The galactic core is gone from November to February, but the air is dry and transparent, Orion is overhead, and the transparency on the night after a cold front passes is the best of the year.

Red light only. Your eyes take twenty minutes to adapt and one phone screen to lose it. Most phones have a red-tint accessibility setting; turn it on before you arrive.

Dress for two hours of standing still. Even in midsummer, a mountain site at two in the morning is cold, and in Hokkaido or Nagano it is seriously cold. The usual failure is not the sky; it is going back to the car after forty minutes.

Check that the road is open. Many of the high roads in Nagano, Gunma and Hokkaido close overnight or close entirely from November to late spring. The gate is not signposted from the bottom.