Jodrell Bank Observatory: Mark II Telescope

Jodrell Bank Observatory: Mark II Telescope

Radio telescope designed in 1960 and built between 1962 and 1964 to the designs of Sir Charles Husband of the structural engineering firm Husband and Company of Sheffield, working to the requirements of Sir Bernard Lovell. The telescope was constructed by Arrol & Co. A new circular bowl surface made of aluminium panels was mounted on top of the original elliptical bowl in 1987.

The structure is constructed primarily of concrete and structural steel, with welded steel sheet and later aluminium panels. The ground-floor base building is circular and houses the roller track and alt-azimuth mount, with a rectangular engine room projecting from the south-east side. A concrete bracket sits on top of the circular base building and supports an elliptical reflector dish. A rectangular first-floor room, the Turntable Lab, is positioned between the base of the bracket, and a separate small engine room, the Elevation Drive Cabin, is situated on the rotating structure of the telescope itself.

The base building, ground-floor engine room (known as the Ward Leonard Room), first-floor central room, and telescope bracket are all constructed of pre-stressed concrete with flat roofs, some covered in asphalt. All windows are fitted with Georgian-wired glazing. The Ward Leonard Room is well-lit by large metal-framed windows. At the centre of the north-west side is a small square projecting room with windows in three elevations. On both sides are wide full-height doorways with timber double doors, the right-hand door featuring a wicket. The circular base building is lit by four horizontal metal-framed windows, with a tall wide doorway on the south side with timber double doors. On the east side, a flight of concrete steps with metal pipe handrails and diamond wiring infill leads up to the roof of the circular building. Metal pipe railings without wiring infill run around the perimeter. The flat-roofed Turntable Lab has concrete braces extending to the outward-leaning telescope bracket and is well-lit by tall vertical metal-framed windows. Wide full-height doorways with timber double doors are positioned at the right-hand ends of both long elevations. The Elevation Drive Cabin, situated on the rotating structure, has a deep concrete engine-bed base with walls and flat roof constructed of riveted steel panels and a sliding steel-panel doorway.

The elliptical reflector bowl has a lattice-work steel frame supported on the concrete bracket with concrete counter-weights positioned to the rear. The elliptical paraboloidal bowl is constructed of welded steel sheet with a major axis of 38.1 metres (125 feet) and a minor axis of 25.4 metres (83 feet 4 inches). This is overlaid by the 1987 circular aluminium panel surface. The aerial, with a focal point of 12 metres (40 feet), is supported by four lattice-work legs standing out from the edge of the bowl structure. The lower right leg incorporates a narrow flight of steps providing access to the aerial focal point, with a hanging flight of steps allowing access from the roof of the Elevation Drive Cabin.

Internally, the Ward Leonard Room contains the original azimuth gearbox on a deep concrete engine bed, since modified, bearing a plaque for Crofts (Engineers) Ltd of Bradford and stamped "AUG 30 62 3Hz". This powers a vertical driveshaft, gear chain and cogs which move rollers controlling the horizontal position of the alt-azimuth mount in the circular base building. On the east side of the gearbox are the two original motors of the control system, now replaced by control cabinets along the south-west side of the room. The circular base building contains the alt-azimuth mount, which sits on 54 steel rollers at a diameter of 12.8 metres (42 feet) on a concrete foundation block in a spoke chamber, with a narrow walkway around the outside. The Turntable Lab contains a central full-height circular cabinet of riveted steel panels known as a "twister", through which telescope wires are threaded to prevent tangling. The room retains the original circular enamelled light shades and includes a small 500-kilogram travelling crane positioned above a trap door in the floor, through which the alt-azimuth mount can be accessed. The Elevation Drive Cabin contains a motor and gearbox which drives a vertical driveshaft controlling the vertical position of the telescope.

The Ward Leonard Motor Generator System, after which the ground-floor engine room is named, was historically the standard system for producing direct current power for rotating the telescope.