Abstract: A vacuum chamber includes chamber walls separating a chamber interior and a chamber exterior, with one or more access ports defined in the chamber walls. A viewing tube extends from the chamber exterior into the chamber interior and terminates in a window. A positioner for imaging devices is then provided within the viewing tube, and is thus situated at least partially within the chamber interior with its imaging device(s) oriented towards the window of the viewing tube to allow imaging of areas within the vacuum chamber. The positioner preferably allows translation and/or rotation of an imaging device within the viewing tube within two perpendicular planes oriented along the axis of the viewing tube, thereby allowing the imaging device to view an area of interest from more angles oriented about the area of interest than would otherwise be possible if the imaging device was situated outside the vacuum chamber.