I'm no expert, but I used a temp gun on my first hatch last month and it saved my eggs. I found out that both my thermometers were off by about 2 degrees. It was a big help.You can't be real sure if your thermometer is working spot on anyway. Do your eggs feel right to you? Most times I go by how they feel. Too warm? Not warm enough? The thermometer does give me an idea when I see where it's at when I am happy with how they feel. I then watch to see if it's reading at that point from there on. Make sense?