Usuda Star Dome, officially known as the Saku City Astronomical Observatory, is a public observatory located in Usuda, Saku City, Nagano Prefecture. Opened on November 29, 1996, the observatory has welcomed astronomy enthusiasts, families, and visitors interested in the mysteries of the universe.
One of its distinctive features is its public nighttime observing sessions. On nights when the facility is open, visitors can join these sessions without making a reservation in advance, an approach that is relatively uncommon among public observatories in Japan.
The observatory was developed in the Usuda area, which is also home to the JAXA Usuda Deep Space Center, following the local declaration of Usuda as a “Town of Stars.” The facility was created to promote astronomy and space-related education and cultural activities within the community. Following the municipal merger in 2005, Saku City took over its management and operation.
The observatory’s main telescope is a 60 cm reflecting telescope manufactured by Mitaka Kohki. It uses a Cassegrain optical system with a 7,200 mm focal length and an F12 focal ratio, allowing visitors to observe a wide range of celestial objects in impressive detail.
Two 20 cm refracting telescopes, also manufactured by Mitaka Kohki, are available for astronomical observations. One has a focal length of 2,000 mm (F10), while the other has a focal length of 2,400 mm (F12).
Together, these telescopes provide opportunities to observe different types of celestial objects and give visitors a closer look at the night sky.
The observatory includes a dedicated training room equipped with a 100-inch screen and multimedia projector. The space is used for astronomy lectures, educational programs, special events, and other activities designed to deepen visitors’ understanding of space.
The area surrounding the observatory has been developed as a park known as the Family Plaza. During the daytime, visitors can enjoy walking and picnicking while surrounded by the natural scenery of Saku, making the site suitable for families as well as astronomy enthusiasts.
General observing sessions are held on evenings when the observatory is open. Anyone can participate, and advance reservations are not required. Visitors can register at the facility on the day of their visit.
When weather conditions are clear, staff members guide visitors as they observe the Moon, planets, star clusters, galaxies, and other celestial objects through the observatory’s telescopes.
For visitors who have rarely had the opportunity to see astronomical objects through a large telescope, an evening at Usuda Star Dome offers a memorable way to experience the scale and beauty of the universe.
The observatory is open from 10:00 a.m. to 10:00 p.m., with final admission at 9:00 p.m..
The observatory is generally closed on Mondays and Tuesdays. When a closure day falls on a national holiday, the following weekday is used as the substitute closing day. It is also closed on the day following national holidays and during the New Year period from December 29 to January 3.
Temporary openings may be scheduled for special events or notable astronomical phenomena.
Admission is 500 yen for adults and 250 yen for elementary and junior high school students. Groups of 20 or more people receive a 20% discount.
From the Saku Interchange on the Joshin-Etsu Expressway or the Saku-Minami Interchange on the Chubu-Odan Expressway, travel toward Nirasaki. From the Isemya intersection on National Route 141, head west for approximately 5 kilometers.
Parking is available at the observatory, making it convenient for visitors traveling by car.
From Usuda Station on the JR Koumi Line, the observatory is approximately 15 minutes by taxi.
The observatory is surrounded by nature, and the journey through the Saku countryside offers changing scenery throughout the seasons.
Usuda Star Dome is a place where visitors of all ages can experience the beauty and mystery of the universe. Its powerful telescopes, educational programs, and public observing sessions make astronomy accessible to both beginners and experienced enthusiasts.
The combination of astronomy and the surrounding natural environment also makes the observatory an enjoyable destination for families. When visiting Saku, consider staying after sunset and looking up at the night sky to experience a different side of Nagano’s highland landscape.