Front of my trimmed laptop back-light flat panel
This is constructed from an old laptop screen, with a dead back-light. I happened to have another Cold Cathode Fluorescent light, from a discarded scanner, so after removing the LCD, I modified the size of the back portion of the display, to fit my lamp. Many of these panels are constructed from a tapered piece of diffractive plexiglass with multiple diffusion screens. Others use a flat piece of plexiglass with small etched dots & several diffusion layers. I found that with my backlight, the diffusion layers had the effect of narrowing the field of view. So once the panel was cut to size and the light installed, I added 2 layers of drafting velum, spaced by~1/4" of Cardboard. This made the illumination very flat and non-directional.
The final layer was a 1/4" thick piece of milk-white plexiglass. On top of this is placed the foam ring, to slide over the dew shield of the scope. Since I had an exciting electrical experience with the inverter, during a previous astrophotography session, I also enclosed this into a small box. The entire panel runs off 12V and is quite portable, as I found, somewhat robust (as long as bulb itself is not broken).