I heat O2 in a steel pipe in my charcoal fire. No electronic equipment, just eyeball and experience. My quenching oil is a large canister of maize oil, and I temper in an electric oven.

Also, while indeed crystalline structures are perfect at a certain temperature, many steels are very tolerant of less than perfect temperatures, as long as you're above the curie point. Even some types of stainless can be done by eyeball in a charcoal fire. And despite the fact that some people say this can not be done, Mike has tested my results and consistently measured 59,5 HRC which is perfect for the kitchen knives that I make.