| Abbreviation | Definition |
|---|---|
| RAPT | Reynolds Amateur Photometry Team |
| RASC | Royal Astronomical Society of Canada |
| RATS | Robot Astronomy Talk Show |
| RC | Relativistic Correction |
| RCI | Rocket Consortium Interstellar |
| RE | ROSAT (ROentgen SATellite) EUV (Extreme Ultra-Violet) |
| REPT | Relativistic Electron-Proton Telescope |
| RFO | Robert Ferguson Observatory |
| RFT | Rich Field Telescope |
| RGO | Royal Greenwich Observatory |
| RGO | Royal Greenwich Observatory (Herstmonceux or Cambridge) |
| RLOF | Roche Lobe OverFlow |
| RMO | Rattlesnake Mountain Observatory |
| RN | Reflection Nebulosity |
| ROG | Royal Observatory, Greenwich |
| ROS | Return Of Saturn |
| RQQ | Radio- Quiet Quasar |
| RQZ | Radio Quiet Zone |
| RSAA | Research School of Astronomy and Astrophysics |
| RSFC | Radially Stratified Flame Core |