Assertion: telescope's mirror | /r/Synonym | subreflector
Facets:
value: near it
type: LOCATION
value: at the prime focus
type: LOCATION
Source sentences:
text: More often, to get the most out of the giant dish’s collecting power, we use a secondary mirror called a subreflector at the prime focus (or near it) to reflect focused waves down into a more convenient location — the center of the dish.