A "secondary mirror" refers to a smaller mirror that is positioned in a telescope, reflecting light from the primary mirror to the eyepiece or camera. It helps magnify and focus the image for observation or capturing pictures. Full definition
Such fast wide - field optics require a radically new design, involving three mirrors: a smaller secondary mirror near the mouth of the telescope and two highly curved mirrors, the primary and tertiary, arranged concentrically at the back end. (discovermagazine.com)
All of its components — its solar power array, sunshield, 6.5 - meter main mirror, and boom - mounted secondary mirror — must unfold perfectly as the spacecraft cruises to its final orbit, 1.5 million kilometers from Earth. (science.sciencemag.org)
In 2012, telescope technicians adapted the 43 - meter to become an Earth station for tracking and downlinking data from Spektr - R, including a high - frequency receiver and a fiber optically - controlled secondary mirror system that could fine tune the focus of the telescope quickly and remotely. (greenbankobservatory.org)