Here is a versatile adapter from Blue Fireball that can be used for prime focus and fixed eyepiece projection photography with your telescope.
Separate the two parts and the lower barrel by itself is a standard 1.25" Prime Focus T-adapter. Insert the 1.25" barrel into your diagonal or telescope, attach your D/SLR camera to the male T-thread (via a T-ring that is specific to your camera; not included), and you are ready to take photos as prime focus with your telescope or spotting scope. In this set-up, the optical chain will be:
Telescope/Diagonal > Prime Focus T-adapter > T-ring > D/SLR camera
Or you can use the complete adapter for fixed eyepiece projection photography. Just insert the 1.25" barrel of the adapter into your diagonal or telescope, and then insert an appropriate eyepiece into the upper barrel. Your camera can then be positioned to shoot the magnified image created by the eyepiece. Again, the camera attaches to the male T-thread at the top of the adapter with an appropriate T-ring for your camera that you provide. In this set-up, the optical chain will be:
Telescope/Diagonal > Fixed Eyepiece Projection T-adapter > 1.25" Eyepiece > T-ring > D/SLR camera
Note that the length of this set-up is not variable. You can change the magnification by switching eyepieces, but for any given eyepiece, the length of the total set-up and the eyepiece magnification factor is "fixed." The silver screw visible in the photos is used to secure the eyepiece inserted into the adapter.
You will be able to use many, but not all, 1.25" eyepieces with this adapter. The adapter barrel can accept 1.25" eyepieces up to 37.5mm (1.47") in maximum outside diameter. The length of the upper barrel of the eyepiece (above the eyepiece shoulder, excluding the lower 1.25" barrel) cannot exceed 36mm (1.42"). Please check your eyepiece dimensions before ordering to ensure that it will fit inside the adapter. Longer eyepieces will stick out of the adapter, but you can use these by adding a T-thread spacer or extension tube (not included) to the adapter to increase its overall length.
The prime focus adapter is threaded to accept standard 1.25" filters so you can use your favorite photography filters as well. Precision machined from aluminum and black anodized. The adapter weighs 3.8oz and its total length is 3.74" (95mm).
The use of this adapter is not limited to D/SLR cameras. It can also be used to image with webcams and video cameras. For this, you will need to attach your webcam to the male T-thread on the adapter via a webcam-to-T thread adapter. Similarly, you can connect a video camera via a C mount-to-T thread adapter. This adapter cannot be used with point-and-shoot cameras.