Stunning images

Tom,
I especially like the composite image showing venus's path.
Sorry to bother you, but I was just wondering how you acheive focus on the 12'' dob,I assume this is prime focus.I recently bought a canon 550d and tried to attach it to the scope via the t ring and 2'' adapter but could not achieve focus.My scope specs are 300X1500 f/5.
Once again,All your photos are ajoy to look at thanks for posting
Regards Orestis