Laser and similar temp non-contact guns are not accurate once the steel starts to glow red. The hotter the steel gets above 1000F brighter the steel glows, and the more inaccurate the readings gets. There are lab guns that can be adjusted, and with some fine tuning can give fairly good readings. These are very expensive, and really only accurate for the thing it was adjusted for. Switch the target object and the accuracy goes away. I have a $1600 temp gun that I mainly use for checking the grill and steaks. I don't consider it accurate enough for doing HT.
When doing HT, if you want accuracy, you need either a HT oven with a controller, or a forge with a PID readout pyrometer. There is a section in the stickys that tells how to hook up your forge for PID control that will give very accurate HT control. A muffle is also a good idea for forge HT. You can start with the PID used as a read-only device to tell what the forge chamber is at, and then can add the parts to control the gas later on.
My two-stage forge control is used by many people who get +/- 2 to 5 degree accuracy in a forge. It works best with a blown burner.
The low cost laser pyrometers at HF and other hardware places are great for checking the quench oil temp, checking the tempering oven temp, and checking on things below 900F. These sell for between $10 and $30. There is little difference between them despite the pricing. I have several around the shop to check all sorts of things. My most used test is to check how hot the outside of the HT oven is. This has saved burned fingertips more than once.
Templi-stix are good for some tasks, but not really suited for doing HT. They can be used to test out the HT oven accuracy or check a PID forge control out. I keep them in 1435, 1450 and 1465. That will tell me if the HT oven is roughly in range. Set the oven to 1425 and program steps at 5 degrees each up to 1475. Have a 5 minute hold at each temp. write 1435/1450/1465 on a piece of steel with the coordinating crayon. Place in the 1425 oven and check after four minutes. Note if the 1425 has changed or not, and return the steel to the oven. Repeat, checking and making notations for each step. You can get a good track graph of the oven actual temp accuracy this way. Adjust your HT regimes accordingly.
