SHOOTING THE MOON
The best subject for trying prime-focus photography is the Moon. Even with slow film, exposures are only a fraction of a second.
The size of the Moon in the frame depends on the scope's focal length. A 2,000 mm focal length tern produces a lunar disk big enough to fill a 35 mm frame. With a 1,000 mm system, the Moon will be about 9 mm across—still impressive.
Because the viewing screens of most cameras go dark at such long focal lengths, the principal challenge is to get the Moon in focus. A camera with an interchangeable focusing screen helps. Matte screens made tor telephotolens work provide a brighter image, making it easier to get that sharp lunar snapshot.