| Abbreviation | Definition |
|---|---|
| CAAA | Capital Area Astronomy Association |
| CAAS | Central Arkansas Astronomical Society |
| CADC | Canadian Astronomy Data Centre |
| CAI | Calcium Aluminum-rich Inclusion |
| CAL | Casual Astronomy League |
| CALL | Collaborative Asteroid Lightcurve Link |
| CAMC | Carlsberg Automatic Meridian Circle |
| CAPER | Conceptual Astronomy and Physics Education Research |
| CASA | Common Astronomy Software Applications |
| CASPER | Collaboration for Astronomy Signal Processing and |
| CASPER | Collaboration for Astronomy Signal Processing and Electronics Research |
| CASU | Cambridge Astronomical Survey Unit |
| CASU | Cambridge Astronomy Survey Unit |
| CBAT | Central Bureau for Astronomical Telegrams |
| CBSAP | Charlie Bates Solar Astronomy Project |
| CCAR | Colorado Center for Astrodynamics Research |
| CCAS | Cape Cod Astronomical Society |
| CCF | Cosmogenic Correlation Factor |
| CCMS | Command, Control, and Monitor System |
| CCSN | core-collapse supranov?? |