Ishigakijima Astronomical Observatory Murikabushi 105cm Telescope

Ishigakijima Astronomical Observatory (石垣島天文台) sits in Ishigaki City, Okinawa Prefecture, and is run by a council of six organisations: the National Astronomical Observatory (part of the National Institutes of Natural Sciences), Ishigaki City, the Ishigaki City Board of Education, the Yaeyama Star Association (a specified NPO), the Okinawa Prefectural Ishigaki Youth House, and the University of the Ryukyus. The site combines public outreach, school and lifelong learning activities, and research uses centred on a large optical–infrared reflector telescope.

Seasonal behaviour and observing windows

The observatory’s latitude is relatively low, which places the ecliptic high in the sky compared with more northerly sites. That geometry makes the facility especially useful for observations of planets and other Solar System objects: outside the general public observing slots the telescope is put to work for planetary science and small‑body studies. The scheduling for public observing sessions and showtimes changes with the seasons, and the observatory adjusts its observing programme accordingly.

Location, management and a brief history

VERA long‑baseline interferometry work on Ishigaki preceded the optical facility: the National Astronomical Observatory established the VERA Ishigaki station (a 20 m radio telescope) and it was opened in March 2002 as one of the VLBI network points. Following requests from local residents and the Yaeyama Star Association, the National Astronomical Observatory decided in May 2004 to install an optical–infrared telescope on Ishigaki. The Ishigakijima Astronomical Observatory was established on a summit on the island in March 2006 and was opened to the public from 1 April 2006. The facility suffered extensive damage from Typhoon No.13 on 15–16 September 2006 and public programmes were suspended; recovery work led to a reopening for general observing on 1 April 2007. Visitor milestones recorded by the observatory include 10,000 visitors by 8 July 2007 and 30,000 by 21 February 2010.

The main telescope: “Murikabushi” and its capabilities

The observatory’s primary instrument is a 105 cm optical–infrared reflecting telescope, manufactured by Nishimura Seisakusho and nicknamed “Murikabushi” (an Okinawan dialect word for the Pleiades). Its optical design is a Ritchey–Chrétien reflector with an effective aperture of 105 cm and a system focal ratio of F/12. The telescope has multiple focal stations:

• a Cassegrain focus used for research (equipped with a cooled CCD camera for photometry),
• Nasmyth focus 1 configured for public viewing,
• Nasmyth focus 2 set aside for research instruments such as spectrographs.

The mount is an altitude–azimuth configuration (keivitai-style), and the telescope operates under automatic control. While observing, the drive range covers elevation angles from 15° to 88° and azimuth from true south ±270°. The dome that houses the instrument is 8 metres in diameter and automatically tracks the telescope during observations. The public viewing station uses standard eyepieces and is designed so that automatic control can present targets to visitors; research foci support instruments such as three‑colour simultaneous photometry cameras.

Facilities and public programmes on site

The site includes an observation facility with an 8 m-diameter dome, an observation room, research laboratories, the telescope dome itself and, since 2013, a dedicated “Star Learning Room.” The Star Learning Room was added in 2013 and opened to the public on 4 July 2013; it is equipped with a 4D2U screening system and a 40 cm equatorially mounted telescope intended for learning and demonstration use.

Daytime facility visits are available without prior reservation. The observatory also runs 4D2U screening sessions (reservation required), night‑time sky observation sessions (reservation required; sessions are held on Saturdays, Sundays and public holidays, with a capacity of around 30 people and arranged in two shifts; times vary by season), and a weekday “Chura‑hoshi Guide Tour” that brings together a guided observation and a 4D2U screening (reservation required). From the entrance to the dome the route is barrier‑free so that wheelchair users can reach the telescope and take part in observing.

Research focus, collaborations and discoveries

Research at the facility concentrates primarily on Solar System targets: planets, comets and asteroids. The observatory also performs observations of transient astronomical phenomena and has contributed to confirmation follow‑ups of gamma‑ray bursts through international observing networks. The island additionally hosts the VERA Ishigaki station (one of the VERA array points), which carries out VLBI observations used to make precise maps of the Milky Way and to measure crustal deformation and plate motions across Japan.

The observatory and its associated projects have links to several named asteroid discoveries: asteroid number 13989 “Murikabushi” was named after the Murikabushi telescope and was discovered by Tsutomu Seki; asteroid (372024) “Ayapani” was discovered in 2008 by a high‑school student who participated in a research experience programme run in connection with the observatory; and (10179) Ishigaki was discovered by Takao Kobayashi and named in reference to the presence of the VERA station on the island.

Visiting: address and transport

Address: 1024‑1 Arakawa, Ishigaki City, Okinawa 907‑0024. From Ishigaki Airport the observatory is a 40‑minute drive by car. There is no public transportation to the site, so visitors use a private car or taxi to reach the facility.

FAQ

What is the observatory's principal telescope?

A 105 cm optical–infrared Ritchey–Chrétien reflecting telescope nicknamed "Murikabushi" with Cassegrain and two Nasmyth foci and an 8 m dome.

Who operates Ishigakijima Astronomical Observatory?

A council of six organisations: the National Astronomical Observatory (part of the National Institutes of Natural Sciences), Ishigaki City, Ishigaki City Board of Education, the Yaeyama Star Association (NPO), the Okinawa Prefectural Ishigaki Youth House, and the University of the Ryukyus.

How do I get there from the airport?

The observatory is a 40‑minute drive from Ishigaki Airport; there is no public transport, so a private car or taxi is necessary.

What programmes are offered to the public?

The observatory offers daytime facility visits without reservation, 4D2U screenings (reservation required), night‑time observation sessions with reservations and limited capacity, and a weekday guided tour that includes observing and 4D2U.