Construction of the Transit Hut, originally known as the Astronomical Observatory, started during May 1913. Its purpose was to take star sights by theodolite to determine Cape Denison’s exact longitude. It was located approximately 30 m to the northeast of the Main Hut, on a 900 mm high rock ledge.
The Hut was constructed of an Oregon frame (with metal shelf brackets assisting in bracing) and lined externally with packing case timbers. The structure had one door in the northeast corner. Additionally, there was a narrow slot in the roof and upper part of the north and south elevations to assist observations. The structure was clad in sheepskin and canvas.
The structure contained a ‘10 inch transit instrument’, given to the expedition by the Government Astronomer. This was positioned on a 225 mm, square timber pillar and set into the rock.