Generic Fine Focusing Knob, increase focusing accuracy and ease Make your stargazing experience better with the Generic Fine Focus Knob, Fits the Celestron 8", 9.25" SCT telescopes. The honeycomb-patterned knob creates a great look while providing exceptional precision for planetary and stellar observations. The 70 mm (2.76 in) diameter Fine Focus Knob fits snugly over your stock focuser, offering fine detail focusing also rapid focusing simultaneously. Focusing capabilities: Stock focus knob: 5 mm turn = 26° focus change Fine focus knob: 5 mm turn = 8° focus change Included: 1 Fine Focusing Knob