| Rezman Observatory | Eslovenia | Tunjice | — |
| Rho Ophiocus observatory | España | Las Rozas de Madrid | — |
| Ricky Observatory | Estados Unidos | Blue Springs | — |
| Ridge A | — | Región del Tratado Antártico | 4.053 m |
| Riethnordhausen Observatory | Alemania | Riethnordhausen, Saxony-Anhalt | — |
 Rihlaperä Observatory | Finlandia | Kypärämäki | — |
| Rikubetsu Astronomical Observatory | Japón | Prefectura de Hokkaido | — |
| Rimbach observatory | Alemania | Rimbach | — |
| Rio Cofio observatory | España | Collado Villalba | — |
 RIT Observatory | Estados Unidos | Nueva York | — |
 Ritter Observatory | Estados Unidos | Ohio | — |
| River Moss Observatory | Estados Unidos | Misuri | — |
| River Oaks Observatory | Estados Unidos | New Braunfels | — |
| River Ridge Observatory | Estados Unidos | Roland | — |
| Riverside observatory | Estados Unidos | Riverside | — |
| Rixeyville observatory | Estados Unidos | Rixeyville | — |
| RMS Observatory | Estados Unidos | Indian Hill | — |
| ROAD observatory | Chile | San Pedro de Atacama | — |
| ROASTERR-1 Observatory | Rumania | Cluj-Napoca | — |
| Robert Brownlee Observatory | Estados Unidos | California | — |
 Robert-Mayer-Volks- und Schulsternwarte Heilbronn | Alemania | Heilbronn | 174 m |
| Robotic Lunar Observatory | Estados Unidos | Flagstaff | — |
| Robotic Optical Transient Search Experiment | Estados Unidos | New Mexico | — |
| Rocca Observatory | Brasil | Jardim Botânico de Brasília | — |
| ROCG observatory | Brasil | Río de Janeiro | — |
| Rochedale (APTA) observatory | Australia | Rochedale | — |
| Rock Finder Observatory | Canadá | Calgary | — |
| Rockland Observatory | Estados Unidos | Sierra Vista | — |
| Roeser Observatory | Luxemburgo | Roeser | — |
| Rogers Observatory | Estados Unidos | Míchigan | — |
| Rokycany Observatory | República Checa | Rokycany | — |
| Rolling Hills Observatory | Estados Unidos | Warrensburg | — |
| Rolvenden observatory | Reino Unido | Rolvenden | — |
| Romito observatory | Italia | La Spezia | — |
| Romney Robinson Memorial Dome | Reino Unido | Condado de Armagh | — |
| ROSA observatory | Francia | Verclause | — |
| Rosarno observatory | Italia | Rosarno | — |
 ROSAT | — | — | — |
| Rose Cottage Observatory | Reino Unido | Keighley | — |
| Rose-Hulman Observatory | Estados Unidos | Terre Haute | — |
| Roseland Observatory | Reino Unido | Cornwall | — |
| Rosemary Hill Observatory | Estados Unidos | Florida | — |
| Roser observatory | España | Blanes | — |
 Rossi X-ray Timing Explorer | — | — | — |
 Rossitten Bird Observatory | Imperio alemán | Fischhausen (district) | — |
| Rotamah Island Bird Observatory | Australia | Victoria | — |
| Rothney Astrophysical Observatory | Canadá | Alberta | — |
| Rouet observatory | Francia | — | — |