365Astronomy Canon EF Lens to T2-Mount Adapter for CCD Camera - CLEARANCE
This adapter allows you to attach most astronomical CCD and CMOS cameras to all Canon EOS lenses including EF-S lenses. This adapter converts the Canon EOS bayonet on the lens to a standard male T2 thread. It is especially recommended for CCD or CMOS cameras with large sensors.
There is also a base with a standard 1/4" photo thread to attach the complete system to a camera tripod or it can be piggy-backed onto the telescope if you've got a photo adapter on the telescope. Many Skywatcher telescopes (and Celestron Newtonian and refractor telescopes) come with a standard 1/4" photo thread on the tube ring and for some telescopes (Celestron SCTs) there is a special piggy-back mount available.
Max theoretical diameter of a CCD or CMOS camera that can fit (due to the distance of the mounting base) is 105m, but it also depends on the shape of the camera and whether an additional T-extension is being used which might place the camera far enough to allow any size of camera to be used behind the adapter... The length of the base is 11mm, so if the distance is more than 11mm, a camera of any size can be attached. This will depend on the distance (depth) of the sensor from the front of the camera.
The flange focal distance of Canon EF and EF-S lenses is 44mm, so you'll have to achieve that distance to the camera's sensor to achieve focus.
Length of extension = 44mm - 19mm (thickness of this adapter) - depth of camera sensor
ZWO ASI CMOS cameras have a depth of sensor at 12.5mm Length of extension = 44mm - 19mm - 12.5mm = 12.5mm, so you'll have to use an extension of 12.5mm length. There is no such extension size available, but the inner part of our variable T-extender will provide just the necessary extension to achieve focus. Alternatively you could use a TS-Optics 5mm extension and a Baader 7.5mm to create such length.
Cooled ZWO cameras have 17.5mm (with the 11mm spacer fitted), so in that case you would need 44mm - 19mm - 17.5mm = 7.5mm extension, which is available from Baader. Click here!
Please note that ZWO ASI cameras also come with a T-mount to C-mount adapter, and as the sensor is comparatively small, you may also consider to use a cheaper Canon lens to C-mount adapter instead of this adapter, however the big advantage of this adapter is that it can be directly attached to a tripod or piggybacked onto a telescope's top. This might be not an advantage though if you use a large telephoto lens that has already got a mounting base. In that case we would still recommend to use this adapter if there is a large sensor in your camera...
A 1.25" filter adapter with M28.5 thread is also included as standard, so unless you use a full frame camera you could also add any standard 1.25" filter to improve your images (i.e. Baader UHC-S, Astronomik CLS, Castell UHC or various OIII or H-alpha filters...)
There is a standard 1/4" photo thread at the base of the adapter to attach it to a photographic tripod or to piggy-back it on top of a telescope...