LSST Light Path

Light from a source in the sky reflects off the three mirror surfaces, and through the refractive lenses. The LSST telescope consists of three aspheric (nonspherical) mirrors: an 8.4-m primary mirror, a 3.5-m convex secondary mirror, and a 5.0-m tertiary mirror. The primary and tertiary mirrors were fabricated from a single piece of Ohara E6 low-expansion glass, resulting in the monolithic LSST Primary/Tertiary Mirror (M1M3) The LSST Secondary Mirror (M2) is the largest convex mirror ever made.