Look at this picture instead of the diagram for step 6:
The alignment of the camera and the slit is off the axis of the unit. We want to be able to point the unit "like a gun" --and add things to the "barrel" (see this photo of foolishness of mine, and see Jeff Warren's note on flare spectrometry.)
Here, we flipped the camera around from Figure 6, and mounted in the center.
cardboard spacers, duct tape, and hot glue have all been used to replace the sticky tape, so that the camera is also centered. Mounting the unit in the center is more for my sanity than anything.
The black cardboard has been flipped around to prevent interior reflections in this case. Scrap back cardboard from the packaging could be added to replace the sticky tape
Questions and next steps
Andy Z took this one home from barnraising 2013. He is interested in flare spectrometry. This unit is labeled "Z."