Mitaka National Astronomical Observatory

photo by おむこさん志望 · CC BY 3.0

Historic 1921 dome and solar telescope: free self-guided visits every day.

The historic seat of the National Astronomical Observatory, with buildings from 1921 onwards registered as cultural properties: the dome of the 20 cm telescope (第一赤道儀室), the solar tower telescope (太陽塔望遠鏡). Entry is open and free every day, without booking for small groups. A special open day in October adds lectures and evening observations to the usual route.

Historic campus of the National Astronomical Observatory of Japan (NAOJ) in Mitaka. Five buildings are registered as 登録有形文化財 (Registered Tangible Cultural Property): the 第一赤道儀室 (dome of the 20 cm telescope, 1921), the 天文台歴史館, the 太陽塔望遠鏡 (solar tower telescope), the 旧図書庫 and the 子午儀資料館, the last of which is also a 重要文化財 (national Important Cultural Property). The campus is still an active research site today; several reviews note that most of the buildings stay closed to the public on ordinary days.

ℹ️ Open every day 10:00–17:00 (entry until 16:30), free, except 28/12–4/1 (confirmed by reading the official page directly in this session). Self-guided visit without booking for small groups: you register at the entrance gatehouse and receive an identification sticker. A closure for electrical maintenance is announced for 14/11/2026. A special open day, ‘三鷹・星と宇宙の日’, is held on 24/10/2026, 10:00–17:00, with lectures and evening observations. The 4D2U theatre requires a separate booking.

🚉 天文台裏 · 3 min walk

Sources: nao.ac.jp · nao.ac.jp · nao.ac.jp

All series · Open the map