The metering structure, which consists of the metering cylinder and the spider arm assembly, is designed to attach the spectrometer to the mirror cell and maintain its position with sufficient accuracy to assure proper focus and alignment. It is constructed of INVAR to minimize the effects of temperature variations. The metering cylinder has a series of light baffles mounted on the inside to reduce scattered light. Various high voltage power supplies and the HUT TV camera are mounted on the spider arms in positions where they block the least amount of incoming light. The relationship between the metering structure and the other components of the telescope can be seen in Figures 1-2 and 2-2.