I had some problem with my 3D-printer and this DIY Flat frame box fell asleep. Now I started it again and have got some very promising result. The key to it is the LED stripe which can be fine adjusted in its color.
Note:
This is only interesting for color cameras. like my DSLR camera.
Here are the details of the project with text and photos:
http://www.astrofriend.eu/astronomy/...alibrator.html
It's working now but I 3D-print some new details that correct the small details.
/Lars