Haterumajima Astronomical Observatory Tower, Astronomical observatory on Hateruma Island, Japan

Haterumajima Astronomical Observatory Tower sits on Japan's southernmost inhabited island, providing views of the night sky with refracting telescopes. The location offers minimal light pollution, making stars from both northern and southern hemispheres clearly visible to visitors.

Built with about 180 million yen from the national Community Island programme, the tower and an adjoining open plaza were completed on 18 May 1994 beside the Japan's Southernmost Point monument at Takana Cape. Salt damage and typhoon flooding repeatedly disabled the telescope and planetarium; it closed in July 2022, and after surveys in 2023 Taketomi Town decided to demolish it.

The tower's name, Haterumajima Hoshizora Kansoku Tower, is used locally for a facility whose rooftop hosted nightly constellation talks (hoshizora gaido) before it closed in July 2022. The island's old calendar life still shapes closures: the tower shut on the lunar date of Mushama, the July 14 old-calendar festival of the island's Bon observances.

The facility has been closed since July 2022 and is slated for demolition, so it cannot be entered. The site lies at Takanazaki in the southeast of Hateruma Island, near the Japan's Southernmost Point Monument, about 15 minutes by car or 40 minutes by rental bicycle from Hateruma Port.

The Southern Cross is fully visible only from late April to mid-June during opening hours, making this Japan's only facility where the complete constellation can be observed. Outside opening hours, the island itself allows sightings from early December to the end of June.