EntityQ35273· pop 37· linked from 599 articlesoptical telescopeSign in to savetelescope which is used to focus light from the visible part of the electromagnetic spectrumConnectionsrefracting telescopeEntityoptical aberrationEntityminute and second of arcEntitylightEntitynebulaEntitylensEntityradianEntitynanometreEntityW. M. Keck ObservatoryEntityangular diameterEntitycurved mirrorEntitycatadioptric systemEntityCassegrain mirror systemEntityNetherlandsConceptSunConceptMoonConceptastronomyEntityIsaac NewtonPersonstarEntitySolar SystemEntityCategoriesOptical devicesOptical telescopesTelescopes