When testing my new Kanthal furnace (I'll open a topic on this later) I let it cool down after the first heat and was curious at what temperature I can see when it still emits light. The room was completely dark and then I looked into the peephole (a stove glass covered hole in the lid) and saw a very very dull red glow and a few minutes later even just a gray glow. The latter is due to that there is too few light to activate the cones in the eye which are responsible for color vision, so only the monochrome rods are (barely) activated. Then I grabbed my infrared pyrometer, opened the lid and saw 480 C which is close to the theoretical value. Did anyone try this ?
Black out your eyes for 30mins, then look. The airforce taught us sayings to keep cones and rods straight. 1. You use your ROD at night 2. Don't eat ice cream cones in the dark. They call this visual purple or rhodopsin. It's what gives us our night vision and it burns off the rods with very little light. So no, I never thought about what the lowest temp I could see was. I would think 480c is about the lowest you could see. Try your neighbors cat, maybe he can get see lower.
