Sky watcher quattro 8s 205mm 8 f800 parabolic dual speed imaging newtonian optical tube assembly the new sky watcher quattro series with their fast f4 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 and stray light is kept out its paraboloidal primary mirror is made of low thermal expans