I can really answer that. It depends on the room temps, the size of the chameleon, basking light wattage. Just remember that really long periods of basking … and I will guess like 45 minutes to an hour (someone please correct me if I’m wrong) is probably too long and the wattage needs to be increased or the distance from the bulb to the chameleon needs to decrease. Just don’t get the bulb really close to the chameleon … you are risking burns that way. I always go with a higher wattage bulb rather then to put the basking light right on the screen.
If the chameleon basks for very short periods, maybe just a few minutes or its skin turns white and/or it gapes with its mouth then the temps are much too warm and the distance from the bulb from the chameleon needs to increase or use a lower wattage bulb. I can’t give you definitive answers really, as I said you need to experiment and be observant.
-roo