Assertion: newtonian telescope's mirror | /r/HasProperty | centered
Facets:
value: accurately
type: MANNER
value: optically
type: MANNER
Source sentences:
text: To be optically centered, the secondary mirror must be offset both in the direction away from the focuser and towards the primary mirror.
text: For exact centering of the optical axis, the secondary mirror must be correctly offset, and the primary mirror must also be accurately centered.