Digiscoping is a method of obtaining photos using a digital camera through a spotting scope, telescope or, less often, binoculars. Afocal projection is a method of astrophotography in which photographs are taken by holding or mounting the camera over the telescope eyepiece, with the camera taking the place of your eye. Afocal projection is the method most commonly associated with digiscoping.
For the best possible results, it is crucial that the optical axis of both the camera and the telescope are aligned. The distance between the camera objective and the telescope eyepiece is also important and typically is adjusted by trial and error. Originally, attaching the camera to the telescope would greatly depend upon the craftsmanship of the photographer, though there are now many commercial adapters available. The quality of the telescope and eyepiece are critical factors. Telescopes that use objectives with special refractive elements and scopes that use a reflex or catadioptric design yield the best results because they control chromatic aberrations well.
Digiscoping is a modern form of astrophotography long practiced by astronomers. Astrophotography is a technique of combining a camera with a telescope to capture images, a standard practice among astronomers. Historically the 35mm SLR or large format film cameras would be used for this purpose. The advent of the digital camera has introduced a new set of issues, with many advantages but a few key disadvantages.
Astronomers tend to take long-exposure photographs of celestial objects and because of this astronomers originally found digital cameras somewhat problematic due to their high inherent sensor noise. This noise limits their usefulness for long-exposures, especially since point-objects, such as stars, can be obscured by even one "hot" pixel. Continuing advancements in digital camera and image manipulation has somewhat overcome this limitation and digiscoping astronomy has become more popular. In daylight situations where long-exposure times are not required, such as birdwatching, the sensor noise issue is not a problem.
Other than the above, for digiscoping astronomy, a proper telescope mounting and tracking mechanism is also essential due to the movement of stars, and long exposure required to capture distant, low light stars.
This technique is also practiced by birdwatchers or birders, as they prefer to be called in the United States. Birders found the digital camera to be a particularly effective addition to their field telescopes and quickly adopted the digiscoping technique. This technique is called digiscope birding, or digi-birding. For this variety of digiscoping, fast shutter speed and minimal shutter delay are more essential due to bird movement.
When not birding, some birders enjoy using their digiscoping equipment to photograph plants (for example, wild orchids growing in the canopy of a jungle), insects (for example, wild bees near their beehive), other shy or dangerous wild animals, or details in old buildings (for example, statues/gargoyles on the roof of old churches/castles).