The lightwave 72 ed r f6 refractor is a portable telescope for imaging and visual use the f6 ed doublet optics feature an ohara s fpl53 ed element and schott glass mated element delivering high contrast elements with good colour correction the dual speed rack and pinion focuser with a 110 ratio fine adjustment knob ensures accurate and easy focusing to ensure images are sharp at the eyepiece or on your camera ccd chip focusing is especially easy in live view mode on a dslr