[Visionoz (Bill)]

From what little I know. the projection tube is supposed to be used as in "eyepiece projection focus" mode - whereas what you're attempting to do is "prime focus" mode ie you connect your camera directly to the end of the telescope where the diagonal/eyepiece usually sits in the drawtube - so perhaps the use of that projection tube will definitely cause you to have no image as its focal point is way too far out

In the eyepiece projection focus mode you would attach one end of that tube to the eyepiece and the other is where your camera gets fitted

Perhaps what I just stated above is all wrong!! and others with better experience will be able to put you on the correct path

HTH
Cheers
Bill