Part of the problem with "regular" thermometers is that they measure air temp, not the temp of surfaces. If the thermometer is too close to a heat source the glass or plastic of the case tends to distort the reading. I really like the non-contact infrared temp guns. They do measure the surface temp of anything you point it at up to a certain distance and as you don't have to leave the entire instrument in the heat for more than a few seconds don't overheat and read abnormally high. If you really want to know what temp the skin of a basking cham is reaching (and I think this is the most important reason for measuring basking temp anyway), use this type of instrument. They are really cheap these days, accurate to within a degree or so, don't disturb the cham, and easy to use.