I've been cursing my laser a bit recently because it's been behaving badly. I can't decide if the tube is on the way out or if it's just because the outside temperature has suddenly heated up significantly. I took another look to make sure that the mirrors and lenses were clean and I discovered this visible smut on one of the mirrors. I know it wasn't there last time I cleaned the mirror and it won't rub off which makes me think that the mirror itself might be damaged now. I hope to hear something from HPC in the morning.