Tried to calibrate the spectrum using a CFL as in the instructions. My displayed spectrum has the same shape but can only align either the 436 or or the 53x (forgot exact number) marker. The whole spectrum ( violet to red) lies on the right side of the ‘box’. I tried to use the start X, end X boxes to center but that didn’t work. I tried moving the webcam in the tube but that didn’t move it to the left much or at all. I can only get the spectrum to rotate.

I tried to push the webcam farther into the tube but could only push a few inches (50mm) using my fingers. If the webcam is not at the end, I lose sight of it in the Theremino display box and it is hard to manipulate the webcam so that the spectrum displays again.

Question, is the tube too long?. It is 18 inches which is 457mm. Would shortening the tube move the displayed spectrum to the left on the Theremino display?