| Nottingham Weather Centre | Reino Unido | — | — |
| Nova Milanese observatory | Italia | Nova Milanese | — |
| Novaloop observatory | Francia | Mougins | — |
| Novi Ligure observatory | Italia | Novi Ligure | — |
| Novoselki observatory | Ucrania | Novosilky | — |
| Novosibirsk Magnetic Observatory | Rusia | — | — |
| NTT Rokko Astronomical Communication Center | Japón | Prefectura de Hyōgo | — |
| Nubbin Ridge Observatory | Estados Unidos | Arkansas | — |
| Nuevos Horizontes observatory | España | condado de Camas | — |
 Nuffield Radioastronomy Laboratory | Reino Unido | — | — |
| Nurmijarvi Magnetic Observatory | Finlandia | — | — |
 NuSTAR | Estados Unidos | — | — |
| Ny-Ålesund NIPR Observatory | Noruega | Nueva Alesund | — |
| Nyenheim observatory | Países Bajos | Güeldres | — |
 Nyrölä Observatory | Finlandia | Nyrölä | 209 m |
 O'Brien Observatory | Estados Unidos | Marine on St. Croix | — |
| OACL observatory | Italia | Teramo | — |
| Oak Bay observatory | Canadá | Oak Bay | — |
 Oak Ridge Observatory | Estados Unidos | Massachusetts | — |
| Oakley Observatory | Estados Unidos | Indiana | — |
| Oakley Southern Sky observatory | Australia | Coonabarabran | — |
| Oakridge Observatory | Estados Unidos | The Hammocks | — |
| Oakwood observatory | Estados Unidos | Oakwood | — |
| OAO University Observatory Station Aras | España | — | — |
| OATU observatory | Brasil | Tupi Paulista | — |
| Oaxaca Observatory | México | Oaxaca | — |
| Oberfrauendorf observatory | Alemania | Glashütte | — |
| Oberwichtrach observatory | Suiza | Oberwichtrach | — |
| Oberwiesenthal observatory | Alemania | Oberwiesenthal | — |
 Obihiro City Children's Hall | Japón | Obihiro | — |
| ObsCT observatory | Italia | Catania | — |
 Observartorio McDonald | Estados Unidos | Fort Davis | 2.077 m |
 Observatoire Astronomique de Mont-Soleil | Suiza | Berna | — |
| Observatoire d'Hettange | Francia | — | — |
| Observatoire de Bédoin | Francia | Bédoin | — |
| Observatoire de Castres | Francia | Castres | — |
| Observatoire de l'Ardeche | Francia | Ardèche | — |
| Observatoire de physique du globe de Clermont-Ferrand | Francia | Aubière | — |
 Observatoire de Saint-Maur | Francia | Saint-Maur-des-Fossés | — |
 Observatoire de Saint-Véran | Francia | Saint-Véran | 2.930 m |
| Observatoire des Cote de Meuse | Francia | Vigneulles-lès-Hattonchâtel | — |
| Observatoire des professions de l'animation | Francia | — | — |
 Observatoire du Mont-Sinaï | Francia | Verzy | — |
| Observatoire du Morne des Cadets | Francia | Saint-Pierre | 250 m |
 Observatoire Marin de la Réunion | Francia | Reunión | — |
 Observatoire Midi-Pyrénées | Francia | Toulouse | — |
 Observatori Astronòmic de Castelltallat | España | San Mateo de Bages | 878 m |
| Observatori de Santa Maria de Montmagastrell | España | Santa Maria de Montmagastrell | 319 m |