Windowless vacuum ultraviolet collimator

We describe a vacuum collimator that we have assembled to characterize the windowless ultraviolet properties of a sounding rocket spectrographic telescope. The collimator comprises a Cassegrain telescope, with SiC coated optics, used in the pre-flight calibration phase of the Far Ultraviolet Spectroscopic Explorer, and vacuum skins provided by NASA/Wallops. The collimator focal plane has a three-axis motorized stage, which we have used for the precision placement of a knife edge focal locator along with pinhole and flat-field sources. We describe the focusing procedure and present the results of a number of experiments whereby the collimator, telescope and spectrograph point spread functions were determined and a spectro-spatial flat-field of the detector was acquired.