Massimo's photoblog

The 6.5m diameter primary mirror of the MMT telescope. Originally, the MMT telescope was made with 6 individual 1m mirrors mounted on the same support (hence the name “Multiple Mirror Telescope”). A few years ago the individual mirrors were substituted with a single 6.5m active mirror, making it one of the largest in the world. Active means that the mirror is supported by a large number of actuators (pistons) which are used to correct the curvature of the mirror to ensure an optimal shape when it points in different parts of the sky. This technique, adopted by modern large telescopes, is called active optics. Adaptive optics is instead a technique to correct for the blurring caused by the atmospheric turbulence using another deformable secondary mirror. The MMTAO system is using a 1m diameter deformable secondary mirror (not mounted at the time I took this photo).

The lights in the backgrounds are the street lights of Green Valley, on the road from Tucson to Nogales, in Mexico.