 Observatorium Tusculanum | Dinamarca | Høje-Taastrup | 32 m |
| Observatory | Estados Unidos | California | — |
 Observatory | Reino Unido | distrito metropolitano de Oldham | — |
| Observatory "Stellar Society" | Bulgaria | Yundola | — |
 Observatory and Planetarium dr. Zdeňka Kvíze | República Checa | Horka Domky | 475 m |
| Observatory At South Wing, St Ibbs, 90 Metres To West South West Of House | Reino Unido | St Ippolyts | — |
| Observatory Circa 100 Yards South West Of Lilburn Tower | Reino Unido | Lilburn | — |
| Observatory for ionospheric research in Kuehlungsborn | Alemania | Kühlungsborn | — |
 Observatory Großschwabhausen | Alemania | Großschwabhausen | — |
 Observatory House | Reino Unido | — | — |
| Observatory Hurtado | Chile | Río Hurtado | — |
 Observatory in Banská Bystrica | Eslovaquia | Banská Bystrica | — |
 Observatory in Boskovice | República Checa | Boskovice | — |
 Observatory in Mikulášovice | República Checa | — | — |
 Observatory in Prague-Podolí | Checoslovaquia | Praga | — |
 Observatory Khureltogoo | — | Bogd Jan Uul | 1.670 m |
 Observatory Ledeč nad Sázavou | República Checa | Ledeč nad Sázavou | — |
 Observatory of Kunstkamera, Saint Petersburg | Rusia | — | 10 m |
 Observatory of Maximilian Hell, Žiar nad Hronom | Eslovaquia | Žiar nad Hronom | 280 m |
| Observatory of Nurol | Francia | Aurec-sur-Loire | 448 m |
| Observatory of Saint-Pardon-de-Conques | Francia | Saint-Pardon-de-Conques | — |
| Observatory of San Vito a Montelupo | Italia | Montelupo Fiorentino | 100 m |
| Observatory of Sciences of the Universe of the University of Paris-Sud | Francia | París | — |
 Observatory of Szeged | Hungría | Szeged | — |
 Observatory of the Collegio Romano | Italia | Roma | — |
 Observatory of the rue Serpente | Francia | — | — |
| Observatory of the State University of Missouri | Estados Unidos | Misuri | — |
 Observatory of university federal of Rio Grande do Sul | Brasil | Porto Alegre | 11 m |
 Observatory Sankt Andreasberg | Alemania | Braunlage | 710 m |
 Observatory TT1 | Italia | Castelgrande | — |
 Observatory Vsetín | República Checa | Vsetín | 385 m |
| Observatory, Kinpurney Hill | Reino Unido | Angus | — |
 Observatory, Museum Gardens | Reino Unido | City of York | — |
| Observatory, Pitfour House Estate | Reino Unido | Aberdeenshire | — |
 Observatório Astronómico da Faculdade de Ciências da Universidade do Porto/Professor Manuel de Barros e respetivas instalações | Portugal | Oliveira do Douro | — |
 Observatório Astronómico da Universidade de Coimbra | Portugal | Santa Clara e Castelo Viegas | — |
| Observatório Astronômico do Sertão de Itaparica | Brasil | Itacuruba | 390 m |
| Observatório Les Engarouines | Francia | Mallemort | — |
 Observatório Municipal de Americana | Brasil | São Paulo | 545 m |
 Observatório Municipal de Campinas Jean Nicolini | Brasil | Campinas | — |
| Observatório Wykrota | Brasil | Minas Geraes | — |
 Observeum Burgum | Países Bajos | Tytsjerksteradiel | — |
| Obserwatorium Astronomiczne Grudziądz | Polonia | Grudziądz | — |
| OCA-Anza Observatory | Estados Unidos | (2061) Anza | — |
| OCA-DLR Asteroid Survey | Francia | Alpes Marítimos | 1.271 m |
| Ochiai observatory | Japón | Ochiai | — |
| Octagon Observatory, Invercauld Road, Braemar | Reino Unido | Aberdeenshire | — |
 Odesa Astronomical Observatory | Ucrania | Odesa | — |