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A few worthwhile suggestions to date, however one thing that might have been overlooked I think.
How white are white LEDs? and how consistant is the colour temp over a spread of output levels. The circuits discussed so far seem to be concerned only with one type of LED or did I miss something?
I'm thinking of constructing a LED illuminated Light Box myself, and I have been tentatively thinking of running R, G, B, Leds bunched to hopefully give a white mix by the time light gets to the diffuser surface. I must confess I do not know how a white Led gets to be white, but if it is some sort of tri colour Led oscillating at a relatively high frequency the it would probably be unsuitable for an Astro-Imaging Light Box. Jerry Lodregus denounces the use of LEDs, but I have not read of his reasons. It might simply be that Red LEDs are not white. In any event I'd suggest that each led needs to be adjustable so that the final diffuser illumination can be tuned to be flat accross the whole usable surface or it just wont work; we don't want bright spots, and we don't want an artificial gradient.
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