Bad news I'm afraid, the distance to the sensor must be pretty precise for camera lenses to focus properly. I can see only three possible fixes.
1. Don't use slr lenses just use it for prime focus astrophotography in a telescope.
2. Buy the clip in filter version of
this clear filter or something similar and hope that it moves the focal plane enough to get focus.
3.Buy a caliper and shims from your local hardware/auto shop and follow the guide again and setting the correct distance for the sensor.