Sunspots shot by eyepiece projection. 130mm aperture f/8 refractor working at f/32 with 18mm Orthoscopic eyepiece projection and a full-aperture Baader solar filter. 1/250th of a second exposure at ISO 400 taken with a Nikon D1H DSLR camera. False color was added in Photoshop.

Normal prime-focus photography uses a camera and lens, or camera and telescope in place of the lens.

Afocal photography uses a camera and lens shooting trough a telescope with an eyepiece.

Eyepiece projection photography uses a camera with no lens on it, and a telescope with an eyepiece.

Eyepiece Projection Adapter and 18mm Orthoscopic Eyepiece

Eyepiece projection photography requires a special adapter that holds an eyepiece at a specific distance from the camera's focal plane. The eyepiece forms an image from the telescope that is projected onto the sensor in the camera. This greatly increases the focal length of the optical system and the magnification, but also greatly increases the focal ratio, requiring longer exposures.

Varying the distance between the eyepiece and focal plane of the camera can increase the magnification of the system, but also requires longer exposures.

For subjects such as close-ups of lunar craters and sunspots (taken with safe solar filtration), the camera's meter can be used and exposure checked with the image display and histogram with the LCD on the back of the camera. For more difficult subjects, such as close double stars, exposures will be determined by trial and error.

See the appendix section on eyepiece projection formulas for calculating magnification, effective focal length and effective focal ratio.