Sky-Watcher Quattro-10CF 250mm (10") f/1000 Parabolic Dual-Speed Imaging Newtonian Carbon Fibre Optical Tube Assembly. The new Sky-Watcher Quattro series with their fast f/4 focal ratios, have been specially designed for high quality astrophotography with short exposure times. They are of course also fine telescopes for visual observations. Their tube interiors have knife-edge ray traced baffles to ensure no light is lost, & stray light is kept out! Its paraboloidal primary mirror is made from low thermal expansion, fast-cooling Pyrex glass.