Thanks Dennis, Alex,
This is hardly an engineering marvel, an old chart-recorder clockwork
mechanism sitting on it's end with a bodged up 1/4 thread

This is more like what would be ideal:
http://www.bmumford.com/photo/rotary/index.html
It wouldn't be beyond me to make one of these either, although I
wouldn't buy the mill rotary table, that could be a simple home
lathe hobbed worm gear etc with a bartel stepper set or PIC micro
with step rates selectable. One day maybe
Alex, I'm thinking of a similar thing.
For now, the huge shroud you see is off the front of a cheap
$49 department store refractor I have

Fits the rubbery perimeter of the 18-55mm lens beautifully.
This is where I would fit some resistors if I did it.
Steve