Using the helical focuser which comes with the LS35 only allows the user to focus with eyepieces, to achieve focus with a video camera such as a DMK, ASI120mm or similar - you need a lower profile one, I use one of these:
http://agenaastro.com/baader-1-25-t2-eyepiece-holder-helical-microfocuser.html
Hope this helps : )
Keith.