Assertion: newtonian telescope's mirror | /r/MadeOf | hole
Facets:
value: usually
type: TEMPORAL
value: in the centre
type: LOCATION
Source sentences:
text: In a symmetrical Cassegrain both mirrors are aligned about the optical axis, and the primary mirror usually contains a hole in the centre thus permitting the light to reach an eyepiece, a camera, or a light detector.
text: In a symmetrical Cassegrain both mirrors are aligned about the optical axis, and the primary mirror usually contains a hole in the centre, thus permitting the light to reach an eyepiece, a camera, or an image sensor.