Assertion: reflecting telescope's mirror | /r/HasProperty | concave parabolic
Facets:
Source sentences:
text: Reflectors have a concave parabolic mirror in the back of the tube.
text: The Gregorian telescope consists of two concave mirrors; the primary mirror (a concave paraboloid) collects the light and brings it to a focus before the secondary mirror (a concave ellipsoid) where it is reflected back through a hole in the centre of the primary, and thence out the bottom end of the instrument where it can be viewed with the aid of the eyepiece.