Abstract: An in-situ optical column comprises: a hollow objective tube; a microscope objective including an outermost lens, the microscope objective inserted at least partway into an objective end of the hollow objective tube with the outermost lens exposed; and a vacuum-tight seal spanning the inside of the hollow objective tube. An ocular lens or digital imaging unit may be disposed at a camera end of the hollow objective tube opposite from the objective end of the hollow objective tube to form an in-situ microscope. The in-situ optical column may include a mounting flange by which the column is mounted to a flange of a vacuum feedthrough of a vacuum system, with the outermost lens of the microscope objective exposed to vacuum of the vacuum chamber and the microscope objective arranged to image a sample disposed on the sample stage of the vacuum system.