is my temp gauge off? 156 degrees F on low basking spot

[Andyurgay]

I have a Zoo Med probe temperature gauge in my guys tank that I move around constantly to check different spots through out the day. As the weather has been getting colder, I noticed my beardie trying to get as close as possible to the bulb so I moved his drift wood so he could get right under the bulb. Since then, he's been resting under the wood or on a rock propped against it. So I rested the probe on a low spot on the wood that he used to favor. It came out to 156 degrees Fahrenheit?! And its at least 9 inches away from the bulb, a 150 watt Zoo Med bulb. His tank is an open 75 gallon. I could never imagine it could get so hot.
So I rested it on the highest basking spot, 3 inches from the bulb, but its to the side, not right under, and it dropped to 109.
Is the probe accurate? Or is it that the low basking spot is directly below the center of the bulb and so the heat is mostly directed down?
Is this dangerous? He seems to move around to regulate just fine. If he's too hot, he moves to the cool side, under the driftwood, to a cool rock or into his cave. He has plenty of room to regulate. But at 150 degrees, I wonder if that's not dangerous? And why is it so hot there? Is the probe just not accurate? I don't want him to accidently cook. It seems a bit extreme.

 

[Andyurgay]

Some background:
He is about 5 inches, nose to vent. I think about 5-6 months old.
Housed in a 75 gallon, open top. Only housed on tile.
Eats veggies daily, dusted. Gets crickets daily, some mealies and roaches when I can make the hour long trip to get them.
The basking light is 4 inches from the highest spot, 11 inches from the ground. Ground temps around 90 degrees, highest spot around 109. Hottest basking 156(?!)
Cool side around 85-90.
Night temp at 78 on the cool side, 83 at night on the basking side.
Basking bulb is a Zoo Med 150 watt.
He has different basking mediums, including natural rock, drift wood, ceramic, all at different heights as well as caves to hide in.
He has pooped at least once a day since I've had him. Sometimes twice. All look healthy but lately, they have been a bit watery.

 

[Luvthemanimal]

Try putting a piex of paper towel on top of the basking spot than the probe and measure the temp... I found the heat bouncing of the object is also read by the prob and not just the heat coming down from the bulb...... Do that see what the difference is... Than remove the paper towel obviously