sentences:  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.One of the problems that restricted the astronomical work of the Observatory during this period was that Balgay Park was enclosed, and the gates were locked at dusk.