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View of the observation window's inner window.

Picture 2 of 3.

The Project Mercury Familiarization Manual notes that the observation window was located above the main instrument panel and consisted of an inner and an outer assembly. The inner window assembly was made up of three glass panes sealed in a titanium frame and attached to the cabin wall. The panes were independently sealed to provide a pressure seal between the panes. The outer window assembly consisted of a glass pane sealed in a titanium frame, attached to the capsule outer skin. The outer window assembly was sealed separately from the inner window assembly, to provide a complete seal. The outer window conformed to the curvature of the capsule conical section.

The spacecraft's inner window was trapezoidal. It was 12.950" long, with the forward end measuring 7.300" and the aft end measuring 9.490" (they were really serious about measuring the size of the window!).

Depending upon the angle from which I photographed the window, it could look especially long or especially squat.