Assertion: reflecting telescope | /r/HasAspect | cage
Facets:
value: at their prime focus
type: LOCATION
Source sentences:
text: Most large reflecting telescopes that are currently in use have a cage at their prime focus that permits the observer to sit inside the telescope tube while operating the instrument.
text: Most large reflecting telescopes that are currently in use have a cage at their prime focus that permits the observer to sit inside the telescope tube while operating the instrument.