CALCULATORS
Camera FOV Calc.    Eyepiece Magnification
A-Focal Photography:  This method is simply holding your camera up to the eyepiece of a telescope and snapping a picture. You may be able to get away with this for daytime shots but for night time or long exposure shots you will likely need an adapter to hold the camera still. To see some of the different adapters that are available, check out this website: http://www.digiscoping.co.uk/?Cat=Adapters
I bought the Baadr style Orion SteadyPix adapter. It will fit 2" and 1.25" eyepieces and virtually any camera. I use 2 different cameras so I needed an adjustable adapter. It works well and is fairly easy to setup. It was well worth the $40 instead of trying to make an adapter.

Once you have an adapter and a telescope you may still have some issues to work around. The first problem that pops up is vignetting! The "vignette" effect is the black halo that appears around the view. The image on the left shows the black shadow called vignette. The image on the right shows how you can use the optical zoom of the camera to get past most of this effect.
Your camera may not be able to zoom past the vignetting though. This brings us to the need for finding cameras that allow us to get good vignette free photos. The reason we get vignette is basically caused because the camera lens is larger than the human eye so it sees a wider picture. The general rule of thumb when selecting a camera is a lower power optical zoom lenses will have a shorter focal point, and shorter distance between the glass and digital ccd sensor. Which is more desirable for digiscoping. The calculator will let you enter your digital camera's specs and determine the angule field of view (aFOV). The goal is to get a camera with a narrower FOV than the eyepiece projects.

The one last concept to address is eye relief. For example, my 32mm Celestron Plossl eyepiece has an eye relief of 22mm. Which means you would need to place your eye 22mm from the glass to see the full picture. This also means your camera lens would need to be 22mm or less from the eyepiece in order to see that full picture. 20mm or higher is considered a LER (long eye relief) but this is helpful for cameras. My Nikon P100 has a lens barrel about 4" long, so the sensor is fairly far back in the camera and it shows a lot of vignetting because the 22mm eye relief isn't long enough.

To explain this, select the Nikon P100 in the calculator below. Then pick the 1/2.3 sensor. For the Scope, select the Celestron C90. Press the "Calc Camera FOV" button. You'll notice the Camera Max Diag FOV is 79.8. The specs on my 32mm eyepiece are aFOV of 45. So there is no chance of seeing a full picture based on the FOV alone. When you couple this with the camera sensor being nearly 4" from the camera lens it produces nearly half vignette. Notice if you change the camera's Min Focal Length from 4.6 to 9mm (how much the camera is zoomed) and recalculate FOV you end up with aFOV of 46.3. So when you zoom in just a tad your aFOV is very close to matching the eyepiece's 45 FOV. This means you get a much fuller picture. If your camera isn't listed in the list below, google the specs and insert them into the fields below and run the same calculations to determine what FOV your camera produces.
 

This calculator was courtesy of jayandwanda.com
Choose a camera model. Make sure the sensor size listed is correct, then click the "Calc Camera FOV" button.
This will show your cameras field of view to the left. Compare this to your listed telescope's aFOV. Remember,
the goal is to have the FOV of the scope to be wider than the camera so your digital camera gets a full picture.
Camera and Scope Data
Scope Aperture (millimeters) Eyepiece Focal Length (mm)
Scope Magnification
Scope Objective Focal Length (millimeters)
Camera Focal Length (millimeters) Horizontal Camera Pixels
Camera f-number Vertical Camera Pixels
Camera Min & Max Focal Length (mm) Megapixels
Camera Min & Max 35mm Equiv Focal Length (mm)

H(mm)   V(mm)

Camera Max & Min Diag. FOV (degrees)
CCD Diagonal (mm) & Pixel "diameter" (mm)
Camera Notes