How is the Alan Gee Mark II connected to the telescope? In order to use it with a Celestron C8 telescope, you need to add the "Baader T2-SC ultra short adapter" 2958500B following this scheme.
You can also use the Alan Gee Mark II in other configurations, for example connecting it into 2" focusers: in this way you can use the focal reducer with many telescopes like Maksutov-Cassegrain, refractors, Schimdt-Cassegrain, etc and, on camera side, you wil have a T2 thread. For this use you need also to use: "T2/2" photographic adapter 2408150" and "T2/T2 inverter ring 1508025"