For years as a birder, I've always thought , "Wow, if only I could get a picture of that!" when seeing some great view of wildlife through a scope. Fortunately, over the past decade or so digiscoping pioneers have been perfecting a practice of coupling a small digital camera in front of a scope eyepiece to take images. The practice has been dubbed "digiscoping" and it is gaining popularity in the birding and other communities every day.
Sometimes the process of placing a camera with a lens behind a telescope or spotting scope is referred to as "image projection" and some digiscopers will also use the term "afocal coupling" two describe the marrying of the circle of light exiting the scope (exit pupil) to the center of the seperate camera lens.
digiscoper at work
In theory, the process is simple enough, you simply mount or hold the camera behind the eyepiece and push the shutter release button to capture your image. However, as you'd expect (or know if you've experimented with this in the past), there is a whole host of variables to control, and field craft tricks that will effect the overall quality of the resultant image. A few of the most logical are as follows:
1) Your image quality will only be as good as the weakest link of your system, so good glass in the camera and scope lenses is essential.
2) not all cameras lend themselves to digiscoping: compact point & shoot cameras with a 4x (sometimes 5x) optical zoom or less seem to be necessary to insure success. It also seems that in most cases, cameras with shorter lens extension perform better than longer-lensed models.
3) while digiscoping allows you to reach incredible levels of magnification, it is safe to say your image quality will generally be better when you are closer to your subject. A lot of atmosphere between you and a distant subject can be full of moisture, dust particles, etc. that will refract light and cause distortion.
Leica APO Televid 82 mm scope, digital adapter 3, and C-Lux camera
Centering the camera on the scope is not necessarily an easy task either, as it requires trying to line up a circle of light at the eyepiece that ranges from ~3.3 mm to 1.6 mm wide only (on the set up above). Scopes with smaller objective lenses will offer even smaller exit pupils . To make matters more complicated, you also need to find the ideal distance between the eyepiece and the camera lens for best results. Due to this, use of an adapter to hold the camera in the proper location is highly recommended.
Leica D-Lux 4 camera
Small digital p&s cameras typical default to a wide-angle view at start up - often near 20-28 mm equivalent. As such, when mounted behind any manufacturers' zoom eyepiece you will see vignetting, a darkened circle around the subject as shown below.
Green-winged Teal, digiscoped with Leica APO Televid 82 mm, showing vignetting
To eliminate vignetting, most digiscopers will run the zoom on the camera up to until the dark circular frame disappears and they get a full-frame rectangular image. With Leica's revolutionary wide-angle 25-50x zoom, this typically requires running the camera zoom up to near the 1x mark (on most cameras I've tried), while other eyepieces with narrower fields of view typical require near 2x magnification on the camera zoom.
With the right camera, you can actually utilize the entire range of magnification on both camera & scope zoom to reach incredible magnifications not typically available in other photographic systems. For example look at the dramatic "before & after" examples provided below. The first image shows how the subject appeared to the unaided eye (e.g. taken at ~50mm lens equivalent).
The image above was taken with the Leica D-Lux camera at full zoom (telephoto) which is the equivalent of a 60 mm lens. Not a lot of power by itself, but when mounted behind the scope this level of magnification is multiplied by the power of magnification on the scope. In this case the scope eyepiece was set to 50x, meaning this image was taken at the equivalent of a 3,000 mm lens (50x 60 mm)! This is amazing since the largest telephoto lens commercially available in most cases is an 800 mm! This digiscoping setup offers nearly 4x the magnification of a very long, heavy, and expensive lens!
I will provide more digiscoping topics in the near future and will try to get increasingly sophisticated to help users of all levels. Just remember, as with anything, practice makes perfect, best to simply have fun and be patient. Feel free to utilize the comment section with questions and perhaps we can get some good information flowing here!