IN THE BEST LIGHT

Kielder Observatory:
A vessel at sea in a rough landscape

It looks like a wooden jetty – seemingly incongruous in its landlocked hillside setting – and that is not all that sets the Kielder Observatory apart from other star-gazing facilities.

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The Kielder Partnership, a public, voluntary and private sector collaboration, promotes Kielder Water and Forest Park as a leisure destination alongside the ongoing forestry activity.

In November 2005, Charles Barclay Architects, a small practice based in South London, beat 229 entrants to win an international competition to build an astronomical observatory at the park, and the project was completed in 2008.

The design brief was for a small observatory with a lifespan of 25 years, to be sited on a very exposed hillside overlooking the park. And the result is the world’s first observatory to use a ‘land-pier’ form and all-timber construction to house two telescopes, specifically for use by amateurs and outreach work.
The design aim was to achieve a positive relationship with its exposed setting, and include all facilities needed in such a remote site.

“Because both telescope housings needed an uninterrupted view of the southern sky, we realised that with an elongated form we could use the slope of the land to set one housing lower than the other,” the architects say. 
“An open decked area between the housings would also allow amateurs to set up their own telescopes during star-gazing events.

“We wanted the experience of being on the observatory to feel like being on a vessel at sea in this rough, open landscape, with an amazing array of stars overhead. The pier strategy also allows for the safe containment of large parties on dark nights when roaming individuals could get lost or injured in the rough terrain.”

Low-tech aesthetic

Timber was chosen early in the process as the primary building material. Besides being a low-carbon material with an obvious relationship with its forest setting, the architects wanted a low-tech engineering aesthetic for the observatory – the opposite of the NASA-inspired world of high tech, high expense and exclusive science.
“We wanted to evoke the curious, ad-hoc structures that have served as observatories down the ages, and to [reference] the timber structures of the rural/industrial landscape at Kielder, the pit props of small coal mines and the timber trestle bridges of the railway that served them. We felt that a beautifully handcrafted timber building with 'Victorian' engineering would be more inspiring in this setting than seamless, glossy domes.”

A major engineering challenge was achieving a stable basis for the rotating turrets housing the two telescopes and the cantilevered elements of the pier structure, which has to withstand very high lateral wind loads.
The substructure is braced with galvanised steel tension rods, attached to head-caps at the top of the columns and ‘shoes’ at the column bases. Often excessive ‘local forces’ would have pulled regular bolted connections out of the timber. The superstructure uses the roof and lateral walls as bracing elements, with stressed skin technology supporting the cantilevered entrance roof and large turret.

The designers say glued plywood skins made the timber framing very rigid, but good quality glued connections were difficult to achieve in poor winter conditions on site. “To their credit, the structural engineers kept the use of steelwork to the absolute minimum in the spirit of a temporary structure that touches the ground lightly.”

Species choices

The original intention was to use timber cut by the Forestry Commission during site clearing, but the fast-growing sitka spruce of Kielder did not have the necessary stiffness or durability. Instead, North American Douglas fir was used for the substructure columns and cantilever beams, Siberian larch for the cladding and the exposed frame elements, and European whitewood for the enclosed frame elements. Spruce and birch plywoods were used for the wall linings and stressed skin elements. 
The timber has been allowed to weather naturally but was pre-treated with fire retardant Non-Com by Arch Timber Protection to give the building some protection against fire.

Detailing includes a broad handrail that serves as a datum for the structure, like a giant spirit level in the landscape. The cladding above it is vertical board-on-board, with horizontal shiplap below, emphasising the continuous horizontal line for the building’s 42 m length.

The original design competition required a building with exemplary ‘eco’ credentials, and the architects say using timber enabled the construction of a sizeable structure at minimal environmental cost, with carbon locked up in the material itself.

The observatory building is entirely self-powered, with a battery system run off a 2.5 kW wind turbine and photovoltaic cells. There is a composting toilet, a wood-burning stove provides heat in a ‘warm room’ and astronomers bring their own water and camping stoves to brew up in the kitchen (water cannot be stored on site because of the sub-zero winter temperatures).

Global warming has brought increased high level cloud that obscures the night sky, so minimising the carbon footprint of the observatory was a priority for the astronomers.

Rotating architecture

The traditional domed form of telescope enclosures was rejected in favour of utilising the self-transforming possibilities of rotating architecture. The turrets sit square to the building when not in use. When closed the building is not obviously an observatory, but resembles an austere, modernist pavilion or belvedere. However, when in use the observatory becomes expressive, with the turrets rotated and shutters open, alive with strange geometries and altered orientations.

The turrets are built off steel octagons with eight wheels that bear on a circular track, itself supported on a stationary steel octagon built on timber framing below. The turning mechanism is a rack-and- pinion, hand-operated by a large stainless steel wheel and handle, with a gearbox to move the six-tonne turrets. The telescopes have concrete-filled tubular steel column mounts – entirely separate from the timber structure to ensure they are vibration-free. Computer-controlled electro-hydraulic servos control the opening and closing sequences of the observatory shutters.

The windy site’s normal power needs are met by the 2.5 kW wind turbine. In calm conditions, 10 130 pW photovoltaic panels keep the 24 deep-cell batteries powered up. There is a dual white and red lighting system, with the red light used during observation to preserve night vision.