 Centro Spaceguard de Bisei | Japón | Bisei | 427 m |
| Cereseto Observatory | Italia | Cereseto | — |
| Cerrina Tololo Observatory | Italia | Murisengo Monferrato | — |
| Cerro del Viento observatory | España | Badajoz | — |
| Cerro Pachón Observatory | Chile | — | — |
| Cerro Tololo-DECam | Chile | Piedras Blancas | — |
| Cerro Tololo-LCO A | Chile | Piedras Blancas | — |
| Cerro Tololo-LCO Aqawan A #1 | Chile | Piedras Blancas | — |
| Cerro Tololo-LCO Aqawan B #1 | Chile | Piedras Blancas | — |
| Cerro Tololo-LCO B | Chile | Piedras Blancas | — |
| Cerro Tololo-LCO C | Chile | Piedras Blancas | — |
| Cesaraugusto observatory | España | Zaragoza | — |
| Cesena Observatory | Italia | Casanova | — |
| Cesson observatory | Francia | Cesson | — |
| Cewanee Observatory at DSNM | Estados Unidos | New Mexico | — |
 Chabot Space and Science Center | Estados Unidos | Oakland | — |
| Chalandray-Canotiers observatory | Francia | Chalandray | — |
| Chambon la Foret Magnetic Observatory | Francia | — | — |
| Changchun Magnetic Observatory | República Popular China | — | — |
| Changchun Observatory | República Popular China | Changchun | — |
 Changgyeonggung Palace Gwancheondae | Corea del Sur | — | — |
 Chankillo | Perú | Casma | — |
| Chante-Perdrix observatory | Francia | Banon | — |
| Chapel Hill observatory | Estados Unidos | Texas | — |
| Charters Towers Magnetic Observatory | Australia | Queensland | — |
| Cheam observatory | Reino Unido | Municipio de Sutton | — |
| Chelford Observatory | Reino Unido | Chelford | — |
| Chelles observatory | Francia | Cantón de Chelles | — |
| Chelmsford observatory | Reino Unido | Chelmsford | — |
| Cheongyang Magnetic Observatory | Corea del Sur | — | — |
 CHEOPS | — | — | — |
 Cherenkov Telescope Array | — | — | — |
| Cherkizovo Observatory | Rusia | Cherkizovo | — |
| Cherokeeridge Observatory | Estados Unidos | Fort Madison | — |
| Cherryvalley Observatory | Irlanda | — | — |
| Chervishevo observatory | Rusia | Chervishevo | — |
| Chicharronian 3C Observatory | España | Tres Cantos | — |
| Chichibu Observatory | Japón | Chichibu | 800 m |
 Chico Community Observatory | Estados Unidos | California | — |
 Chilbolton Observatory | Reino Unido | Chilbolton | — |
| CHILESCOPE | Chile | — | — |
| CHILESCOPE Observatory | Chile | Río Hurtado | — |
| China-Iceland Arctic Science Observatory | Islandia | Þingeyjarsveit | — |
| Chinese Culture University observatory | República de China | Shilin District | — |
| Chinese Hα Solar Explorer | República Popular China | — | — |
| Chinese Virtual Observatory | República Popular China | — | — |
| Chinle observatory | Estados Unidos | condado de Apache | — |
| Chinon observatory | Francia | Chinon | — |