Assertion: telescope's objective | /r/HasProperty | mirror
Facets:
Source sentences:
text: The idea that the objective, or light-gathering element, could be a mirror instead of a lens was being investigated soon after the invention of the refracting telescope.
text: The main objective in a reflecting telescope is a mirror whereas the main objective in a refracting telescope is a lens.
text: Objectives can be a single lens or mirror, or combinations of several optical elements.