Assertion: newtonian telescope's mirror | /r/HasProperty | spherical
Facets:
value: for ease of manufacturing
type: PURPOSE
Source sentences:
text: If the mirror is spherical but with defects such as bumps or depressions, the defects appear greatly magnified in height.
text: All telescopes which utilize both mirror and lens optics require some type of corrector lens when the primary mirror is a spherical surface design.
text: Modern variants may have a hyperbolic primary for increased performance (for example, the Ritchey–Chrétien design); and either or both mirrors may be spherical or elliptical for ease of manufacturing.