the world > physical sensation > sight and vision > optical instruments > mirror > [noun] > speculum (5)
the mirror in a reflecting telescope which receives and reflects the rays of light from the object.
An object made of metal. A metal mirror of an astronomical reflecting telescope. Obsolete.
spec. A metallic mirror forming part of a reflecting telescope.
A polished or coated surface which is curved so as to reflect light in various specific ways; †a lens or burning glass (obsolete). Cf. speculum, n. 2.
Astronomy. A mirror forming part of a reflecting telescope. Cf. sense 3.