 Red Global de Telescopios del Observatorio Las Cumbres | Goleta | — |
| Red Mountain Observatory | Utah | — |
| Redondo Beach observatory | Redondo Beach | — |
| Reynolds Observatory | Nueva York | — |
| Ricky Observatory | Blue Springs | — |
 RIT Observatory | Nueva York | — |
 Ritter Observatory | Ohio | — |
| River Moss Observatory | Misuri | — |
| River Oaks Observatory | New Braunfels | — |
| River Ridge Observatory | Roland | — |
| Riverside observatory | Riverside | — |
| Rixeyville observatory | Rixeyville | — |
| RMS Observatory | Indian Hill | — |
| Robert Brownlee Observatory | California | — |
| Robotic Lunar Observatory | Flagstaff | — |
| Robotic Optical Transient Search Experiment | New Mexico | — |
| Rockland Observatory | Sierra Vista | — |
| Rogers Observatory | Míchigan | — |
| Rolling Hills Observatory | Warrensburg | — |
| Rose-Hulman Observatory | Terre Haute | — |
| Rosemary Hill Observatory | Florida | — |
| Rusty Mountain Observatory | Queen Valley | — |
| Rutherford observatory | Nueva York | — |
 Rutherfurd Observatory | Manhattan | — |
| S.O.S. observatory | Minneapolis | — |
| Sabino Canyon Observatory | Tucson | — |
| Saguaro Observatory | Tucson | — |
| Salida observatory | Salida | — |
| San Clemente observatory | San Clemente | — |
| San Emigdio Peak observatory | California | — |
| San Juan Magnetic Observatory | — | — |
| San Pedro Valley Observatory | Benson | — |
| Sandia View observatory | Río Rancho | — |
| Sandlot observatory | Kansas | — |
| Santana Observatory | California | — |
 SARA-KP | Arizona | 2.133 m |
 Satélite de Sondeo de Exoplanetas en Tránsito | — | — |
| Sayre Observatory | South Bethlehem | — |
| Scott Observatory | Fitchburg | — |
| Seagrave Memorial Observatory | — | — |
 Sears Tower – Harvard Observatory | Cambridge | — |
 Servicio internacional de latitud | — | — |
| Shasta Valley Observatory | Gazelle | — |
 Shattuck Observatory | Nuevo Hampshire | — |
| Shed of Science South observatory | Pontotoc | — |
| Sheep Hill Observatory | Boonton | — |
| Sherzer Observatory | Míchigan | — |
| Shumagin Magnetic Observatory | — | — |