An insulator for an electric heater is configured to allow a heater coil to expandcontract uniformly, and permit an easy fitting of the heater coil thereto. An example apparatus includes a downhole tool having a body defining an outer surface and a plurality of standoffs distributed about the outer surface. The optical apparatus is directed up-and-down and right-and-left by movable pieces connected to movable coils of the VCMs, so as to constitute the turntable device.