@TechConnectify It's easy to see why those were to incredibly popular for smaller and dimmer images. After all, as you explain, the setup process is quick and almost fun. At least compared to it's bigger competitors, the Eidophor. It used Schlieren Projection of an oil film onto which you drew the image with an electron beam. https://www.youtube.com/watch?v=5783jPTKzjk Since you cannot use a getter inside those tubes, you had to replace the cathode every 100 hours, through an airlock.