On Oct 11, 2004, at 7:54 PM, Martin McCormick wrote:

> I have heard of shift registers being used along with feedback
> to generate a pseudo-random bit pattern.

there is some C code to do 5 PWM "random" outputs on a 12c675 here:
    http://www.geocities.com/westfw/electronics/flames.c

It's supposed to look like fire.  It worked pretty well, IMO.
On the other hand, I would think stars would be different.  In
particular, fire spends a lot of time down near zero brightness,
whereas stars, if they twinkle at all, tend to have very brief
lessenings of brightness, along the lines of
	brightness = min(128, 255-random(128))  (where 128 is max brightness)

BillW

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