Celestial equator;0; 
Celestial poles;124; 
Celestial sphere;275; 
Centrifugal force;421; 
Cepheids;486; 
Chandrasekhar limit;588; 
Charge-coupled-device (CCD);736; 
Chromosphere;841; 
Circumpolar stars;932; 
Classification of galaxies;1057; 
Comet nucleus;1251; 
Comet;1175; 
Compass;1314; 
Composite image;1362; 
Compound;1441; 
Concave;1575; 
Conjunction;1685; 
Constellation;1796; 
Convection zone;1927; 
Convection;1851; 
Convex;2042; 
Coordinates;2131; 
Copernicus;2218; 
Core shadow;2281; 
Corona;2350; 
Cosmology;2428; 
Cosmos;2527; 
COSTAR;2614; 
Crab nebula;2741; 
Crust;2905; 
Culmination;2965; 
Cycle;3066; 
Dark matter;3125; 
Dark nebula;3242; 
Declination;3336; 
Deformation;3416; 
Density;3498; 
Diffraction;3551; 
Distance module;3630; 
Doppler effect;3727;