Assertion: telescope | /r/CapableOf | use two hyperbolic mirrors
Facets:
value: to remove both spherical aberration
type: PURPOSE
value: to remove coma
type: PURPOSE
Source sentences:
text: After that, telescopes used mostly the Ritchey–Chrétien design, using two hyperbolic mirrors to remove both spherical aberration and coma, leaving only astigmatism, giving a wider useful field of view.