Sky-Watcher Explorer-150P Parabolic Reflector OTASkyWatcher Explorer 150P 150mm (6") f 750 Parabolic Newtonian Reflector Optical Tube Assembly. All Sky Watcher Black Diamond Newtonian Reflectors feature 0. 5mm ultra thin secondary mirror supports to reduce diffraction spikes and light loss, and high quality Paraboloidal primary mirrors to eliminate spherical aberration. The mirrors are parabolised' to bring all the light rays to the same focal point to produce sharp, contrasty images which are full