Digiscoping is bird photography that combines the magnifying power of a spotting scope with a digital camera.
Digiscoping has become a very popular method for taking photographs of birds. The technique involves marrying a digital camera to a spotting scope. The combination provides extreme magnification for photographing distant birds. When using top quality spotting scopes (prices can range from about $2000 to almost $5000) the quality of the resultant images can be little short of spectacular. Some digital cameras can also capture short segments of video, a feature that can also be used when digiscoping.
Several of the top spotting scope manufacturers have posted video clips on YouTube that demonstrate the technique.
Nikon - Nikon tutorial on Digiscoping / Telescopic lenses
Photography 
