A triangular frame metering structure includes three side beams and three end pieces each connected between two of the side beams. Each end piece top and bottom is configured for connection of support loads, with all support loads connecting to the metering structure at the top or bottom of one of the end pieces. Secondary mirror focusing mechanisms mounted on the end piece tops support pairs of secondary mirror struts. Strut mounts on the end piece bottoms provide connections to pairs of primary mirror struts, base struts, and instrument struts. All support loads connected to the metering structure are thus connected only to the corners of the metering structure and are connected at a same radial distance from a central longitudinal axis. The metering structure has reduced mass with high stiffness for supporting large aperture telescopes.