🌐EnglishEnglishDeutschFrançaisItalianoPolskiPortuguêsTiếng Việt中文EntityQ1439729· pop 8· linked from 13 articlesFoucault knife-edge testoptical test for curved mirrorsConnectionsInternational Standard Book NumberEntityWayback MachineEntityCategoriesAmateur astronomyMeasuring instrumentsMirrorsOptical devicesTelescopes