Abstract: The present invention relates to feeding liquid oxygen from the main condenser of the upper rectifying column of an air liquefying/separating unit into a xenon condensing column. The liquid oxygen is evaporated in varying amounts in correspondence to fluctuating amounts of liquid oxygen being fed into the xenon condensing column. The level and pressure of the liquid at the xenon condensing column is controlled and quantities of liquid oxygen is vented from the xenon condensing column at a constant level. The vented liquid oxygen is exchanged to high pressure oxygen gas in order to evaporate it, and this evaporated gaseous oxygen is supplied to a xenon absorptive column, and recovered as liquid oxygen through heat-exchangers.

Abstract: A function-conversion device for a ground monocular telescope of an erecting-prism type ground monocular telescope. The device includes a rotational plate so mounted as to be horizontally movable in a vicinity of the focal plane of the objective lens of the telescope, with a plurality of windows being provided in the rotational plate and with a reticle and/or a visibility diphragm or a second objective lens being mounted in alignment with the windows. This arrangement provides a convenient and easy-to-handle function-conversion device since the windows can be selectively moved into the vicinity of the focal plane.