When searching I stumbled upon a Chinese site which sells a 'Blast Furnace Top Camera' which should withstand 2000 C for long periods of time. I thought 'How do they handle this ?'. No specifications of the used material for its casing are given. What kind of unobtanium do they use ? Molybdenum ? Tungsten ? Iridium ? And the viewport window must be made of diamond as that is the only transparent material withstanding 2000 C. https://en.itvrb.com/product/159.html If this were real, then many steel plants use such cams inside their blast furmaces, EAF or other high temperature equipment. Any ideas on this ?