aplanatic objective
不晕物镜，齐明物镜

• cover
• coverage
• covered wire
• cover glass
• cover-glass gauge
• cover-glass thickness
• covering power
• cover plate
• cowling
• crack
• cracking
• cradle
• craft
• Cramer-Rao inequality
• cramp
• crank
• cranked eyepiece
• crankshaft
• crank web
• crater
• cratering effect
• crater lamp
• cratoer lamp
• creep
• apparent focus