In the dome, the original telescope given by the Mills Trust was an 18-inch (45 cm.) Newtonian reflector by Grubb Parsons, electrically driven. The dome itself, also built by Grubb, is hand-operated and made of papier-mâché on a framework of steel. The only part of the dome which has had to be replaced over the years is the shutter, where the papier-mâché perished and marine plywood was substituted. The 18-inch telescope was rarely used at full aperture, due to its tendency to be affected by reflections from street lights caused by the open lattice-work tube.