Assertion: eyepiece | /r/CapableOf | provide observer
Facets:
value: with the ability
type: OTHER
Source sentences:
text: Eyepieces, which are used with both refractors and reflectors (see below Reflecting telescopes), have a wide variety of applications and provide observers with the ability to select the magnification of their instruments.
text: To calculate the magnification any eyepiece will offer the observer, divide the telescope's focal length (in millimeters) by the eyepiece focal length (also in millimeters).