Hi- I have mine on a 12hr cycle. I use a $5 timer from homedepot, and have it set to turn on @ 8am and off at 8pm. They are sensitive to other lights and will not sleep if the room is lit up, but there cage lights are off, it must be dark for them the sleep, at least for my panthers! Hope this helps.
:what time your you guys truning your chameleon's lights and what time do they go off? does it matter if the cage is in a living area where there will be other lights?