SO i picked up a small iEQ30Pro to manage the 6D and Sigma 150-600mm lens. The mount is beautiful and works well even if second hand. It mounts the camera flawlessly and also is able to run for 3-5 mins unguided !  

The lagoon and triffid at 500mm on 6D iso 1600 - 10 x 3 min exposures unguided