Former Kurashiki Observatory Sliding Roof Observation Room

Japan's First Public Observatory, Moved Across Town

The Former Kurashiki Observatory Sliding Roof Observation Room (旧倉敷天文台スライディングルーフ観測室) is the 1926 observing hut of Kurashiki Observatory, now standing in the Life Park Kurashiki grounds in Fukuda-cho, Kurashiki City, Okayama Prefecture, and was registered as a Registered Tangible Cultural Property (structure) on August 28, 2001. Its gabled roof slides apart east and west to open the sky.

The Agency for Cultural Affairs records it as a single-storey timber building partly of brick, with a sheet-iron roof and a building area of 24 square metres; its registration number is 33-0053. It originally stood at 2-19-10 Chuo in central Kurashiki. In 2013 Kurashiki City acquired it from the Kurashiki Observatory foundation and moved and restored it at Life Park Kurashiki.

An Observatory for Everyone

In the Taisho era, Japan's observatories were state institutions, and ordinary people rarely got near a telescope. Kurashiki Observatory was founded on November 21, 1926 by Hara Sumiji, a businessman and former town mayor, who paid for it himself after being won over by Kyoto Imperial University professor Yamamoto Issei and the Okayama amateur astronomer Mizuno Senri. The Astronomical Society of Japan describes it as the first private observatory in Japan built to be open to the public.

The observation room housed a British-made 32-centimetre reflecting telescope, described by the Astronomical Society of Japan as a Calver reflector and one of the largest in the country at the time, and it was open to all. Public viewing nights were held here, and the society notes a record of 350 people turning out during one comet observation. The telescope itself is now a Kurashiki City cultural property kept at the Hara Sumiji and Honda Minoru Memorial Hall at the original observatory site.

Honda Minoru, who joined the observatory in 1941 and went on to discover 12 comets and 11 novae, also observed from this room, according to Kurashiki City.

Why It Was Registered

The Former Kurashiki Observatory Sliding Roof Observation Room was registered in 2001 under the criterion of being difficult to reproduce. The Agency for Cultural Affairs notes its fame as Japan's first private observatory and its sliding roof, and calls it valuable in the history of science.

In March 2024 the Astronomical Society of Japan recognised "Kurashiki Observatory and Related Heritage" as Japan Astronomical Heritage, with this observation room listed alongside the observatory itself.

How the Roof Opens

The Kurashiki observation room measures 4.4 metres east-west by 5.3 metres north-south. A brick base 1.1 metres high carries a clapboard-clad timber frame with an eaves height of 2.2 metres. The gabled roof is sheathed in iron sheet; turning a geared handle inside slides each half down along the slope of the gable, east and west (Kurashiki City).

The Agency for Cultural Affairs notes that the telescope stood on its own foundation, separate from the building, so that the shudder of the roof and the footsteps of visitors would not reach the instrument. From outside, that tall base is the first thing you notice about this modest-looking hut.

The Kurashiki Science Center website offers a 45-second video of the sliding roof opening. Watching it before you go makes it much easier to read the building on site.

Visiting the Kurashiki Observation Room

The Former Kurashiki Observatory Sliding Roof Observation Room is an outdoor exhibit of the Kurashiki Science Center within Life Park Kurashiki. The exterior can be seen during the center's opening hours, 9:00 a.m. to 5:15 p.m. (last entry 4:45 p.m.), closed Mondays (or the following day after a public holiday). We found no notice of regular interior access.

By public transport, take Shimoden bus route 51 (for JR Kojima Station via Otaka and Gokenya) from stop 5 at JR Kurashiki Station, about 25 minutes, to Life Park Kurashiki Nishi-iriguchi, then walk about 20 minutes; the fare is 440 yen. By car it is about 15 minutes from Mizushima Interchange on the Seto-Chuo Expressway (ETC only). There are 430 free parking spaces, locked after closing.

The original observatory in central Kurashiki keeps the 32-centimetre telescope in its Hara Sumiji and Honda Minoru Memorial Hall.