The C-mount adapter is designed for mounting a digital camera in the eyepiece tube of a microscope instead of the eyepiece. First, you install the adapter into the tube, then the C-mount adapter, and finally the digital camera into it. The adapter magnification is 0.37x. The maximum field of view without vignetting can be obtained with 1/4" to 1/3" sensors.
Recommended for obtaining the maximum possible field of view on cameras: