I have one on the basking area. I just was an idiot and read it as "put the digital thermometer on the tortoise's back, and let it sit for an hour." Man, I really should have read that sentence again before posting.
I have a laser thermometer that I use to measure around the enclosure to spot check, in addition to digital thermometer/hygrometers on the hot and cold sides. I can't say that I've shined it directly on the shell surface. What shell temp do you shoot for while basking?
When I take temperature readings from around the enclosure, the ExoTerra seems to behave more like the floodlight example than the spotlight. As I keep making adjustments, I may change it around yet again, but at the moment with what I have on hand, it seems to be providing heat to a large...
100w bulb. About 16 inches from the basking spot, so maybe 18-19 inches from the substrate. With the temp gun, the basking spot is mid-90s, substrate surface all around it is in the low to mid 80s. I initially tried a 150w bulb at the same distance, but the basking spot was getting above 100F...
I'll second using the Exoterra Intense bulbs. I redid the lighting in my Russian's enclosure, and tried one of the extra basking lights I had lying around for my bearded dragon. The basking area is in the mid-90s, and it nicely sets up a temperature gradient through the enclosure.