An apparatus and method for thermal imaging of an interior space of a high temperature furnace through an opening in a wall of the furnace. An outer housing houses at least a portion of a rigid borescope. The outer housing has a port for aspirating ambient air through the outer housing to cool the rigid borescope and passing the air through a hole at the end of the outer housing and into the furnace. A camera is operatively connected to a rigid borescope but is located such that it is isolated from the air passing through the outer housing.