Depends on the size of the enclosure, the ambient temperature and the time of day.
I use a spot lamp (as well as a UVB lamp) during the day, positioned at the top and to one side of each enclosure. I could use a ceramic bulb, but they seem to like to see the lighted warm spot. The ambient termperature of the room in which I keep the enclosures is about 70-75F during the day and ranges from 63 to 69F at night (depends a lot on time of year). The area under the spot lamp reaches 95 during the day. It is on a timer, coming on a little after the UVB and going off a little before the UVB lamp.
In the winter, when the ambient room temperature is generally at 64F at night, I have a ceramic lamp that comes on after the spot lamp goes off, and stays on for several hours, turns off (timer) at about 2am until about 4am, then comes back on until the spot light comes on. This ensures that the upper areas of the enclosure never get too cold, but does also allow for a cooler night temp than day temp.
I use multiple combo humidty temperature guages, positioned both near the top and near the bottom of several cages. These guages retain highest and lowest temperature numbers. I review these high/low figures almost daily, to ensure the coldest and hottest moments are not outside my chameleons safe zones.
hope this helps
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Sandra
BC Canada