A vessel dissector for harvesting a target vessel has a tubular member carrying a blunt transparent tip with a terminus for blunt dissection of tissue and a base affixed to the tubular member. An active ring set has first and second ring segments mounted to distal ends of respective manipulator bars in the tubular member. The ring segments juxtapose to define a closed loop with an inner diameter larger than the outside diameter of the tip base. The ring segments are movable between a retracted position nested at the base and respective extended positions distally forward of the terminus. At least one of the ring segments is energizable to cut and cauterize a cylindrical pedicle including the target vessel. The ring segments independently extend longitudinally to provide a variable gap between the ring segments to capture, cut, and cauterize side branches to the target vessel between the ring segments.
