Abstract: This invention relates to a wide angle viewing system (V) which may be inserted into a high temperature environment, in particular, a furnace or burner (F). The superior interior wide angle view (A) yields pertinent information for use in diagnosing combustion problems. The access to the interior from the outside is variable from one furnace or burner to another. The viewer, therfore, was designed so that the wide angle view is retained regardless of the distance (D) the observer (O) must be from the outside to the interior. The wide angle viewer is simply affixed to the end of a pipe or tube (24) of sufficient length to reach to the interior (26), and then inserted into the interior (26) where the observer (O) looks into the rear end (24r) of the pipe to view the interior (26). Photographic equipment may also be installed at the rear end of the tube to provide a pictorial documentation of the interior (26).