Ishigaki Island Observatory - Observing the Southern Cross in Japan's First Starry Sky Reserve

Overview

Ishigaki Island Observatory is a research facility of the National Astronomical Observatory of Japan located in Ishigaki City, Okinawa Prefecture. It features the largest optical-infrared reflector telescope in the Kyushu and Okinawa region, the 105-centimeter "Murikabushi" (which means "group star" or "Pleiades" in Yaeyama dialect).

In 2018, the land area of Iriomote-Ishigaki National Park was certified as Japan's first "Starry Sky Reserve (Dark Sky Park)" by the International Dark-Sky Association (IDA). As Japan's only observatory positioned at a low latitude of 24°north, it uniquely allows observation of southern constellations and the Southern Cross, which are invisible from Honshu.

Observation Environment

Ishigaki Island is positioned approximately 2,000 kilometers southwest of Honshu in a subtropical climate. Befitting its entire designation as a starry sky reserve, dark locations on the island maintain Bortle scale class 2 darkness.

The defining characteristic is the low latitude of 24°north. Southern constellations that set below the horizon in Honshu (latitude ~35°north) achieve sufficient altitude for observation from Ishigaki Island. From December through June, the Southern Cross appears above the horizon, and Omega Centauri in Centaurus becomes observable under favorable conditions.

Furthermore, observing 84 of all 88 constellations year-round is a privilege unique to the Yaeyama Islands in Japan.

Facilities and Usage Information

Celestial observation events using the "Murikabushi" telescope are held by reservation. The 105-centimeter light-gathering power provides impressive observations of planets and nebulae.

Events are held Tuesday through Saturday nights but require advance registration through the official website.

Access

About 40-50 minutes by car from Naha Island Ishigaki Airport, and about 15 minutes by car from Ishigaki Port Terminal. The observatory is located near the summit of Maeseyama Mountain; while the access road is paved, it features steep grades.

Observation Tips

December through early June are optimal for Southern Cross observation, best seen from locations with open southern horizons. The subtropical climate brings high humidity in summer, causing telescope and camera lenses to fog easily—condensation prevention is essential. Winter sometimes brings strong northern winds, but the observatory provides comfortable observation conditions.