This is a classic light box.

The overall housing is from a cardboard box used to carry 5 x 500 sheets of A4 office paper. The box was trimmed to obtain rectangular cross-section.

Interior of the box was lined with 3mm thick foam-core-paper used by artists and architects. Two diffusing screens were made from a sheet of matted polystyrene plastic.

Interior of the box was lit by 4 ultra-bright white LED diodes pointing upwards - light emitted from the diodes lit the box and only the reflected and diffused light was illuminating the screens. Therefore, a very uniform illumination of the external diffuser screen was achieved. The key to this even illumination is the depth of the box, which allows all LEDs to illuminate the rear panel.

A 12V powered brightness adjusting circuity was placed in a corner of the box, as in all my designs - with reverse polarity and over-voltage protection :-)

The box is pretty lightweight and can be easily attached on top of my telescope pointing upwards. Used to flatten FSQ, FS60 etc.

For the small aperture, 4 bright LEDs proved well enough, with light frames in the range of 1s for L, 3s for RGB and maybe 15s for Ha.

If done for the second time, I would make it suitable for a bit larger aperture and would add ultra-bright RED diodes emitting in 650nm region, to get shorter exposures for flats in Ha.